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        Module&nbsp;qmanager
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<h1 class="epydoc">Source Code for <a href="qmanager-module.html">Module qmanager</a></h1>
<pre class="py-src">
<a name="L1"></a><tt class="py-lineno">  1</tt>  <tt class="py-line"><tt class="py-docstring">"""</tt> </tt>
<a name="L2"></a><tt class="py-lineno">  2</tt>  <tt class="py-line"><tt class="py-docstring">QManager is an abstracted Django manager which filters via custom queries.</tt> </tt>
<a name="L3"></a><tt class="py-lineno">  3</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L4"></a><tt class="py-lineno">  4</tt>  <tt class="py-line"><tt class="py-docstring">Introduction</tt> </tt>
<a name="L5"></a><tt class="py-lineno">  5</tt>  <tt class="py-line"><tt class="py-docstring">============</tt> </tt>
<a name="L6"></a><tt class="py-lineno">  6</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L7"></a><tt class="py-lineno">  7</tt>  <tt class="py-line"><tt class="py-docstring">The ``QManager`` class is a subclass of ``django.db.models.Manager`` which can</tt> </tt>
<a name="L8"></a><tt class="py-lineno">  8</tt>  <tt class="py-line"><tt class="py-docstring">remove some of the boilerplate in manager definitions. Managers may be used to</tt> </tt>
<a name="L9"></a><tt class="py-lineno">  9</tt>  <tt class="py-line"><tt class="py-docstring">define 'table-level' operations on your models, and one of their most common</tt> </tt>
<a name="L10"></a><tt class="py-lineno"> 10</tt>  <tt class="py-line"><tt class="py-docstring">uses is to provide a pre-defined ``QuerySet`` for model data. The typical</tt> </tt>
<a name="L11"></a><tt class="py-lineno"> 11</tt>  <tt class="py-line"><tt class="py-docstring">programming idiom goes something like this:</tt> </tt>
<a name="L12"></a><tt class="py-lineno"> 12</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L13"></a><tt class="py-lineno"> 13</tt>  <tt class="py-line"><tt class="py-docstring">    1.  Define your custom manager as a subclass of</tt> </tt>
<a name="L14"></a><tt class="py-lineno"> 14</tt>  <tt class="py-line"><tt class="py-docstring">        ``django.db.models.Manager``, overriding the ``get_query_set`` method</tt> </tt>
<a name="L15"></a><tt class="py-lineno"> 15</tt>  <tt class="py-line"><tt class="py-docstring">        to return a filtered query set. For example::</tt> </tt>
<a name="L16"></a><tt class="py-lineno"> 16</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L17"></a><tt class="py-lineno"> 17</tt>  <tt class="py-line"><tt class="py-docstring">            class MyManager(models.Manager):</tt> </tt>
<a name="L18"></a><tt class="py-lineno"> 18</tt>  <tt class="py-line"><tt class="py-docstring">                def get_query_set(self):</tt> </tt>
<a name="L19"></a><tt class="py-lineno"> 19</tt>  <tt class="py-line"><tt class="py-docstring">                    return super(MyManager, self).get_query_set().filter(</tt> </tt>
<a name="L20"></a><tt class="py-lineno"> 20</tt>  <tt class="py-line"><tt class="py-docstring">                        field1='x', field2='y')</tt> </tt>
<a name="L21"></a><tt class="py-lineno"> 21</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L22"></a><tt class="py-lineno"> 22</tt>  <tt class="py-line"><tt class="py-docstring">    2.  On your model, instantiate the manager. Following from the previous</tt> </tt>
<a name="L23"></a><tt class="py-lineno"> 23</tt>  <tt class="py-line"><tt class="py-docstring">        example::</tt> </tt>
<a name="L24"></a><tt class="py-lineno"> 24</tt>  <tt class="py-line"><tt class="py-docstring">            </tt> </tt>
<a name="L25"></a><tt class="py-lineno"> 25</tt>  <tt class="py-line"><tt class="py-docstring">            class MyModel(models.Model):</tt> </tt>
<a name="L26"></a><tt class="py-lineno"> 26</tt>  <tt class="py-line"><tt class="py-docstring">                field1 = models.CharField(...)</tt> </tt>
<a name="L27"></a><tt class="py-lineno"> 27</tt>  <tt class="py-line"><tt class="py-docstring">                field2 = models.CharField(...)</tt> </tt>
<a name="L28"></a><tt class="py-lineno"> 28</tt>  <tt class="py-line"><tt class="py-docstring">                ...</tt> </tt>
<a name="L29"></a><tt class="py-lineno"> 29</tt>  <tt class="py-line"><tt class="py-docstring">                objects = models.Manager() # Default manager instance.</tt> </tt>
<a name="L30"></a><tt class="py-lineno"> 30</tt>  <tt class="py-line"><tt class="py-docstring">                my_mgr = MyManager() # Custom manager instance.</tt> </tt>
<a name="L31"></a><tt class="py-lineno"> 31</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L32"></a><tt class="py-lineno"> 32</tt>  <tt class="py-line"><tt class="py-docstring">Usage of ``QManager``</tt> </tt>
<a name="L33"></a><tt class="py-lineno"> 33</tt>  <tt class="py-line"><tt class="py-docstring">=====================</tt> </tt>
<a name="L34"></a><tt class="py-lineno"> 34</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L35"></a><tt class="py-lineno"> 35</tt>  <tt class="py-line"><tt class="py-docstring">The problem with this pattern is that it ends up being repeated several times</tt> </tt>
<a name="L36"></a><tt class="py-lineno"> 36</tt>  <tt class="py-line"><tt class="py-docstring">for each model as you try to define several useful custom managers for each</tt> </tt>
<a name="L37"></a><tt class="py-lineno"> 37</tt>  <tt class="py-line"><tt class="py-docstring">type of data. The ``QManager`` class abstracts this idiom by providing a simple</tt> </tt>
<a name="L38"></a><tt class="py-lineno"> 38</tt>  <tt class="py-line"><tt class="py-docstring">way of defining managers to return query sets. Now, what originally involved</tt> </tt>
<a name="L39"></a><tt class="py-lineno"> 39</tt>  <tt class="py-line"><tt class="py-docstring">two parts is now down to one::</tt> </tt>
<a name="L40"></a><tt class="py-lineno"> 40</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L41"></a><tt class="py-lineno"> 41</tt>  <tt class="py-line"><tt class="py-docstring">    class MyModel(models.Model):</tt> </tt>
<a name="L42"></a><tt class="py-lineno"> 42</tt>  <tt class="py-line"><tt class="py-docstring">        field1 = models.CharField(...)</tt> </tt>
<a name="L43"></a><tt class="py-lineno"> 43</tt>  <tt class="py-line"><tt class="py-docstring">        field2 = models.CharField(...)</tt> </tt>
<a name="L44"></a><tt class="py-lineno"> 44</tt>  <tt class="py-line"><tt class="py-docstring">        ...</tt> </tt>
<a name="L45"></a><tt class="py-lineno"> 45</tt>  <tt class="py-line"><tt class="py-docstring">        objects = models.Manager()</tt> </tt>
<a name="L46"></a><tt class="py-lineno"> 46</tt>  <tt class="py-line"><tt class="py-docstring">        my_mgr = QManager(Q(field1='x', field2='y'))</tt> </tt>
<a name="L47"></a><tt class="py-lineno"> 47</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L48"></a><tt class="py-lineno"> 48</tt>  <tt class="py-line"><tt class="py-docstring">As you can see, a custom manager is defined by passing ``QManager``'s</tt> </tt>
<a name="L49"></a><tt class="py-lineno"> 49</tt>  <tt class="py-line"><tt class="py-docstring">``__init__`` method a ``Q`` object. ``Q`` objects are used in Django to specify</tt> </tt>
<a name="L50"></a><tt class="py-lineno"> 50</tt>  <tt class="py-line"><tt class="py-docstring">queries of arbitrary complexity, and by using ``QManager`` you don't need to</tt> </tt>
<a name="L51"></a><tt class="py-lineno"> 51</tt>  <tt class="py-line"><tt class="py-docstring">write all the boilerplate of the first example: all it takes is a simple ``Q``</tt> </tt>
<a name="L52"></a><tt class="py-lineno"> 52</tt>  <tt class="py-line"><tt class="py-docstring">object.</tt> </tt>
<a name="L53"></a><tt class="py-lineno"> 53</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L54"></a><tt class="py-lineno"> 54</tt>  <tt class="py-line"><tt class="py-docstring">Conjunctions and Disjunctions</tt> </tt>
<a name="L55"></a><tt class="py-lineno"> 55</tt>  <tt class="py-line"><tt class="py-docstring">-----------------------------</tt> </tt>
<a name="L56"></a><tt class="py-lineno"> 56</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L57"></a><tt class="py-lineno"> 57</tt>  <tt class="py-line"><tt class="py-docstring">Another feature of ``Q`` instances is that they can be combined using the ``&amp;``</tt> </tt>
<a name="L58"></a><tt class="py-lineno"> 58</tt>  <tt class="py-line"><tt class="py-docstring">(and) and ``|`` (or) logical operators. These must not be the Python literal</tt> </tt>
<a name="L59"></a><tt class="py-lineno"> 59</tt>  <tt class="py-line"><tt class="py-docstring">``and`` and ``or`` operators, as they behave differently to the symbols. Let's</tt> </tt>
<a name="L60"></a><tt class="py-lineno"> 60</tt>  <tt class="py-line"><tt class="py-docstring">say, for example, that you have two query sets defined by ``Q`` instances whose</tt> </tt>
<a name="L61"></a><tt class="py-lineno"> 61</tt>  <tt class="py-line"><tt class="py-docstring">intersection (logical *and*) you want to find. Each of these query sets would</tt> </tt>
<a name="L62"></a><tt class="py-lineno"> 62</tt>  <tt class="py-line"><tt class="py-docstring">be defined by an instance of ``Q``, like so::</tt> </tt>
<a name="L63"></a><tt class="py-lineno"> 63</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L64"></a><tt class="py-lineno"> 64</tt>  <tt class="py-line"><tt class="py-docstring">    query1 = Q(public=True)</tt> </tt>
<a name="L65"></a><tt class="py-lineno"> 65</tt>  <tt class="py-line"><tt class="py-docstring">    query2 = Q(confirmed=True)</tt> </tt>
<a name="L66"></a><tt class="py-lineno"> 66</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L67"></a><tt class="py-lineno"> 67</tt>  <tt class="py-line"><tt class="py-docstring">Each of these return query sets which contain those records which are public</tt> </tt>
<a name="L68"></a><tt class="py-lineno"> 68</tt>  <tt class="py-line"><tt class="py-docstring">and confirmed, respectively. Such query sets would be obtained by calling the</tt> </tt>
<a name="L69"></a><tt class="py-lineno"> 69</tt>  <tt class="py-line"><tt class="py-docstring">``filter`` method on one of the model's managers (i.e. ``objects``). Suppose</tt> </tt>
<a name="L70"></a><tt class="py-lineno"> 70</tt>  <tt class="py-line"><tt class="py-docstring">you now want to find all the records which are both public *and* confirmed, in</tt> </tt>
<a name="L71"></a><tt class="py-lineno"> 71</tt>  <tt class="py-line"><tt class="py-docstring">one query set. Typically, you would define a ``Q`` instance such as</tt> </tt>
<a name="L72"></a><tt class="py-lineno"> 72</tt>  <tt class="py-line"><tt class="py-docstring">``Q(public=True, confirmed=True)``, but this violates the DRY principle, as the</tt> </tt>
<a name="L73"></a><tt class="py-lineno"> 73</tt>  <tt class="py-line"><tt class="py-docstring">same information is repeated. Instead, one may simply do this::</tt> </tt>
<a name="L74"></a><tt class="py-lineno"> 74</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L75"></a><tt class="py-lineno"> 75</tt>  <tt class="py-line"><tt class="py-docstring">    query3 = query1 &amp; query2</tt> </tt>
<a name="L76"></a><tt class="py-lineno"> 76</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L77"></a><tt class="py-lineno"> 77</tt>  <tt class="py-line"><tt class="py-docstring">This is a shortcut which allows you to cut down the amount of extra code you</tt> </tt>
<a name="L78"></a><tt class="py-lineno"> 78</tt>  <tt class="py-line"><tt class="py-docstring">write, and maintain DRY in your code. The ``QManager`` class provides a wrapper</tt> </tt>
<a name="L79"></a><tt class="py-lineno"> 79</tt>  <tt class="py-line"><tt class="py-docstring">which lets you do the same thing in your manager definitions. An example might</tt> </tt>
<a name="L80"></a><tt class="py-lineno"> 80</tt>  <tt class="py-line"><tt class="py-docstring">be::</tt> </tt>
<a name="L81"></a><tt class="py-lineno"> 81</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L82"></a><tt class="py-lineno"> 82</tt>  <tt class="py-line"><tt class="py-docstring">    class MyModel(models.Model):</tt> </tt>
<a name="L83"></a><tt class="py-lineno"> 83</tt>  <tt class="py-line"><tt class="py-docstring">        public = models.BooleanField()</tt> </tt>
<a name="L84"></a><tt class="py-lineno"> 84</tt>  <tt class="py-line"><tt class="py-docstring">        confirmed = models.BooleanField()</tt> </tt>
<a name="L85"></a><tt class="py-lineno"> 85</tt>  <tt class="py-line"><tt class="py-docstring">        ...</tt> </tt>
<a name="L86"></a><tt class="py-lineno"> 86</tt>  <tt class="py-line"><tt class="py-docstring">        public_objects = QManager(Q(public=True))</tt> </tt>
<a name="L87"></a><tt class="py-lineno"> 87</tt>  <tt class="py-line"><tt class="py-docstring">        confirmed_objects = QManager(Q(confirmed=True))</tt> </tt>
<a name="L88"></a><tt class="py-lineno"> 88</tt>  <tt class="py-line"><tt class="py-docstring">        public_confirmed = public_objects &amp; confirmed_objects</tt> </tt>
<a name="L89"></a><tt class="py-lineno"> 89</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L90"></a><tt class="py-lineno"> 90</tt>  <tt class="py-line"><tt class="py-docstring">Flexibility of ``QManager``</tt> </tt>
<a name="L91"></a><tt class="py-lineno"> 91</tt>  <tt class="py-line"><tt class="py-docstring">---------------------------</tt> </tt>
<a name="L92"></a><tt class="py-lineno"> 92</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L93"></a><tt class="py-lineno"> 93</tt>  <tt class="py-line"><tt class="py-docstring">This use of ``&amp;`` and ``|`` is not restricted to just ``QManager`` instances;</tt> </tt>
<a name="L94"></a><tt class="py-lineno"> 94</tt>  <tt class="py-line"><tt class="py-docstring">``Q`` objects may also be combined with ``QManager`` instances via the logical</tt> </tt>
<a name="L95"></a><tt class="py-lineno"> 95</tt>  <tt class="py-line"><tt class="py-docstring">operators. A caveat, however: in these statements, the ``QManager`` instance</tt> </tt>
<a name="L96"></a><tt class="py-lineno"> 96</tt>  <tt class="py-line"><tt class="py-docstring">*must* come before the ``Q`` instance. It is valid, for example, to do this::</tt> </tt>
<a name="L97"></a><tt class="py-lineno"> 97</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L98"></a><tt class="py-lineno"> 98</tt>  <tt class="py-line"><tt class="py-docstring">    public_confirmed = public_objects &amp; Q(confirmed=True)</tt> </tt>
<a name="L99"></a><tt class="py-lineno"> 99</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L100"></a><tt class="py-lineno">100</tt>  <tt class="py-line"><tt class="py-docstring">It is an error, however, to do the following::</tt> </tt>
<a name="L101"></a><tt class="py-lineno">101</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L102"></a><tt class="py-lineno">102</tt>  <tt class="py-line"><tt class="py-docstring">    public_confirmed = Q(confirmed=True) &amp; public_objects</tt> </tt>
<a name="L103"></a><tt class="py-lineno">103</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L104"></a><tt class="py-lineno">104</tt>  <tt class="py-line"><tt class="py-docstring">It is advisable to ensure that errors like these do not happen, as they will be</tt> </tt>
<a name="L105"></a><tt class="py-lineno">105</tt>  <tt class="py-line"><tt class="py-docstring">difficult to debug if they do: an error will most likely be raised somewhere in</tt> </tt>
<a name="L106"></a><tt class="py-lineno">106</tt>  <tt class="py-line"><tt class="py-docstring">the ``Q`` class, rather than for ``QManager``.</tt> </tt>
<a name="L107"></a><tt class="py-lineno">107</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L108"></a><tt class="py-lineno">108</tt>  <tt class="py-line"><tt class="py-docstring">Exclusive Queries</tt> </tt>
<a name="L109"></a><tt class="py-lineno">109</tt>  <tt class="py-line"><tt class="py-docstring">-----------------</tt> </tt>
<a name="L110"></a><tt class="py-lineno">110</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L111"></a><tt class="py-lineno">111</tt>  <tt class="py-line"><tt class="py-docstring">Another feature of query set manipulation is exclusion. ``QuerySet`` and</tt> </tt>
<a name="L112"></a><tt class="py-lineno">112</tt>  <tt class="py-line"><tt class="py-docstring">``Manager`` instances have ``exclude`` methods which, when called with a ``Q``</tt> </tt>
<a name="L113"></a><tt class="py-lineno">113</tt>  <tt class="py-line"><tt class="py-docstring">object, will return the set of all data *not* matching the conditions given in</tt> </tt>
<a name="L114"></a><tt class="py-lineno">114</tt>  <tt class="py-line"><tt class="py-docstring">the query. This is called finding the *complement* of a set of data, and</tt> </tt>
<a name="L115"></a><tt class="py-lineno">115</tt>  <tt class="py-line"><tt class="py-docstring">``QManager`` instances support this through the inversion operator (``~``). For</tt> </tt>
<a name="L116"></a><tt class="py-lineno">116</tt>  <tt class="py-line"><tt class="py-docstring">example::</tt> </tt>
<a name="L117"></a><tt class="py-lineno">117</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L118"></a><tt class="py-lineno">118</tt>  <tt class="py-line"><tt class="py-docstring">    class MyModel(models.Model):</tt> </tt>
<a name="L119"></a><tt class="py-lineno">119</tt>  <tt class="py-line"><tt class="py-docstring">        ...</tt> </tt>
<a name="L120"></a><tt class="py-lineno">120</tt>  <tt class="py-line"><tt class="py-docstring">        public_objects = QManager(Q(public=True))</tt> </tt>
<a name="L121"></a><tt class="py-lineno">121</tt>  <tt class="py-line"><tt class="py-docstring">        non_public_objects = ~public_objects</tt> </tt>
<a name="L122"></a><tt class="py-lineno">122</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L123"></a><tt class="py-lineno">123</tt>  <tt class="py-line"><tt class="py-docstring">If a reference to a ``QManager`` instance, whether through their definition</tt> </tt>
<a name="L124"></a><tt class="py-lineno">124</tt>  <tt class="py-line"><tt class="py-docstring">(i.e. ``~QManager(...)``) or a variable (i.e. ``~public_objects``), is</tt> </tt>
<a name="L125"></a><tt class="py-lineno">125</tt>  <tt class="py-line"><tt class="py-docstring">prepended with a ``~`` symbol, then it's ``__invert__`` magic method will be</tt> </tt>
<a name="L126"></a><tt class="py-lineno">126</tt>  <tt class="py-line"><tt class="py-docstring">called. In the case of ``QManager`` instances, this will return a new instance</tt> </tt>
<a name="L127"></a><tt class="py-lineno">127</tt>  <tt class="py-line"><tt class="py-docstring">whose query is defined as the complement of the old query. This may be used in</tt> </tt>
<a name="L128"></a><tt class="py-lineno">128</tt>  <tt class="py-line"><tt class="py-docstring">conjunction with the other operators, for example::</tt> </tt>
<a name="L129"></a><tt class="py-lineno">129</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L130"></a><tt class="py-lineno">130</tt>  <tt class="py-line"><tt class="py-docstring">    class MyModel(models.Model):</tt> </tt>
<a name="L131"></a><tt class="py-lineno">131</tt>  <tt class="py-line"><tt class="py-docstring">        ...</tt> </tt>
<a name="L132"></a><tt class="py-lineno">132</tt>  <tt class="py-line"><tt class="py-docstring">        public_objects = QManager(Q(public=True))</tt> </tt>
<a name="L133"></a><tt class="py-lineno">133</tt>  <tt class="py-line"><tt class="py-docstring">        non_public_confirmed = confirmed_objects &amp; ~public_objects</tt> </tt>
<a name="L134"></a><tt class="py-lineno">134</tt>  <tt class="py-line"><tt class="py-docstring">        non_confirmed_public = ~confirmed_objects &amp; public_objects</tt> </tt>
<a name="L135"></a><tt class="py-lineno">135</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L136"></a><tt class="py-lineno">136</tt>  <tt class="py-line"><tt class="py-docstring">Using ``QManagerFactory`` for Refactoring ``QManager`` Definitions</tt> </tt>
<a name="L137"></a><tt class="py-lineno">137</tt>  <tt class="py-line"><tt class="py-docstring">------------------------------------------------------------------</tt> </tt>
<a name="L138"></a><tt class="py-lineno">138</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L139"></a><tt class="py-lineno">139</tt>  <tt class="py-line"><tt class="py-docstring">A common design pattern which emerges when using ``QManager`` is the definition</tt> </tt>
<a name="L140"></a><tt class="py-lineno">140</tt>  <tt class="py-line"><tt class="py-docstring">of queries which apply to several similar models. For example, if several of</tt> </tt>
<a name="L141"></a><tt class="py-lineno">141</tt>  <tt class="py-line"><tt class="py-docstring">your models have ``public`` fields which are boolean flags telling whether or</tt> </tt>
<a name="L142"></a><tt class="py-lineno">142</tt>  <tt class="py-line"><tt class="py-docstring">not a record is public, then you may want a manager to get only public records.</tt> </tt>
<a name="L143"></a><tt class="py-lineno">143</tt>  <tt class="py-line"><tt class="py-docstring">Because, however, you are defining managers across several models, the query</tt> </tt>
<a name="L144"></a><tt class="py-lineno">144</tt>  <tt class="py-line"><tt class="py-docstring">``Q(public=True)`` will be repeated several times. If, one day, you decide to</tt> </tt>
<a name="L145"></a><tt class="py-lineno">145</tt>  <tt class="py-line"><tt class="py-docstring">change the field to being called ``is_public``, then each query will have to be</tt> </tt>
<a name="L146"></a><tt class="py-lineno">146</tt>  <tt class="py-line"><tt class="py-docstring">edited individually. A typical set-up might look something like this::</tt> </tt>
<a name="L147"></a><tt class="py-lineno">147</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L148"></a><tt class="py-lineno">148</tt>  <tt class="py-line"><tt class="py-docstring">    class A(models.Model):</tt> </tt>
<a name="L149"></a><tt class="py-lineno">149</tt>  <tt class="py-line"><tt class="py-docstring">        public = models.BooleanField()</tt> </tt>
<a name="L150"></a><tt class="py-lineno">150</tt>  <tt class="py-line"><tt class="py-docstring">        ...</tt> </tt>
<a name="L151"></a><tt class="py-lineno">151</tt>  <tt class="py-line"><tt class="py-docstring">        public_objects = QManager(Q(public=True))</tt> </tt>
<a name="L152"></a><tt class="py-lineno">152</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L153"></a><tt class="py-lineno">153</tt>  <tt class="py-line"><tt class="py-docstring">    class B(models.Model):</tt> </tt>
<a name="L154"></a><tt class="py-lineno">154</tt>  <tt class="py-line"><tt class="py-docstring">        public = models.BooleanField()</tt> </tt>
<a name="L155"></a><tt class="py-lineno">155</tt>  <tt class="py-line"><tt class="py-docstring">        ...</tt> </tt>
<a name="L156"></a><tt class="py-lineno">156</tt>  <tt class="py-line"><tt class="py-docstring">        public_objects = QManager(Q(public=True))</tt> </tt>
<a name="L157"></a><tt class="py-lineno">157</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L158"></a><tt class="py-lineno">158</tt>  <tt class="py-line"><tt class="py-docstring">As you can see, because the managers are defined on different models they may</tt> </tt>
<a name="L159"></a><tt class="py-lineno">159</tt>  <tt class="py-line"><tt class="py-docstring">not be reused. A simple way around this is to use the ``QManagerFactory``</tt> </tt>
<a name="L160"></a><tt class="py-lineno">160</tt>  <tt class="py-line"><tt class="py-docstring">function in this module. At the top of your models file (or a separate file for</tt> </tt>
<a name="L161"></a><tt class="py-lineno">161</tt>  <tt class="py-line"><tt class="py-docstring">managers, if you wish), place the following line::</tt> </tt>
<a name="L162"></a><tt class="py-lineno">162</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L163"></a><tt class="py-lineno">163</tt>  <tt class="py-line"><tt class="py-docstring">    PublicManager = QManagerFactory(Q(public=True), name='PublicManager')</tt> </tt>
<a name="L164"></a><tt class="py-lineno">164</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L165"></a><tt class="py-lineno">165</tt>  <tt class="py-line"><tt class="py-docstring">``PublicManager`` will now be a class, with the name 'PublicManager' (due to</tt> </tt>
<a name="L166"></a><tt class="py-lineno">166</tt>  <tt class="py-line"><tt class="py-docstring">the ``name`` keyword), which is a subclass of ``QManager``, and has the</tt> </tt>
<a name="L167"></a><tt class="py-lineno">167</tt>  <tt class="py-line"><tt class="py-docstring">``query`` attribute pre-defined as ``Q(public=True)``. On each model, you now</tt> </tt>
<a name="L168"></a><tt class="py-lineno">168</tt>  <tt class="py-line"><tt class="py-docstring">only need to place the following::</tt> </tt>
<a name="L169"></a><tt class="py-lineno">169</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L170"></a><tt class="py-lineno">170</tt>  <tt class="py-line"><tt class="py-docstring">    class A(models.Model):</tt> </tt>
<a name="L171"></a><tt class="py-lineno">171</tt>  <tt class="py-line"><tt class="py-docstring">        public = models.BooleanField()</tt> </tt>
<a name="L172"></a><tt class="py-lineno">172</tt>  <tt class="py-line"><tt class="py-docstring">        ...</tt> </tt>
<a name="L173"></a><tt class="py-lineno">173</tt>  <tt class="py-line"><tt class="py-docstring">        public_objects = PublicManager()</tt> </tt>
<a name="L174"></a><tt class="py-lineno">174</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L175"></a><tt class="py-lineno">175</tt>  <tt class="py-line"><tt class="py-docstring">And likewise for ``B``. For more information on the ``QManagerFactory``</tt> </tt>
<a name="L176"></a><tt class="py-lineno">176</tt>  <tt class="py-line"><tt class="py-docstring">function, you are advised to consult its docstring and source code.</tt> </tt>
<a name="L177"></a><tt class="py-lineno">177</tt>  <tt class="py-line"><tt class="py-docstring"></tt> </tt>
<a name="L178"></a><tt class="py-lineno">178</tt>  <tt class="py-line"><tt class="py-docstring">For more information, esp. implementation details, consult the source code. It</tt> </tt>
<a name="L179"></a><tt class="py-lineno">179</tt>  <tt class="py-line"><tt class="py-docstring">may also be useful to look at the official Django documentation for the ``Q``</tt> </tt>
<a name="L180"></a><tt class="py-lineno">180</tt>  <tt class="py-line"><tt class="py-docstring">class and database API.</tt> </tt>
<a name="L181"></a><tt class="py-lineno">181</tt>  <tt class="py-line"><tt class="py-docstring">"""</tt> </tt>
<a name="L182"></a><tt class="py-lineno">182</tt>  <tt class="py-line"> </tt>
<a name="L183"></a><tt class="py-lineno">183</tt>  <tt class="py-line"><tt class="py-keyword">import</tt> <tt class="py-name">django</tt> </tt>
<a name="L184"></a><tt class="py-lineno">184</tt>  <tt class="py-line"><tt id="link-0" class="py-name" targets="Variable qmanager.OLD_VERSION=qmanager-module.html#OLD_VERSION"><a title="qmanager.OLD_VERSION" class="py-name" href="#" onclick="return doclink('link-0', 'OLD_VERSION', 'link-0');">OLD_VERSION</a></tt> <tt class="py-op">=</tt> <tt class="py-name">django</tt><tt class="py-op">.</tt><tt class="py-name">VERSION</tt><tt class="py-op">[</tt><tt class="py-number">0</tt><tt class="py-op">]</tt> <tt class="py-op">==</tt> <tt class="py-number">0</tt> </tt>
<a name="L185"></a><tt class="py-lineno">185</tt>  <tt class="py-line"><tt class="py-keyword">try</tt><tt class="py-op">:</tt> </tt>
<a name="L186"></a><tt class="py-lineno">186</tt>  <tt class="py-line">    <tt class="py-keyword">from</tt> <tt class="py-name">django</tt><tt class="py-op">.</tt><tt class="py-name">db</tt><tt class="py-op">.</tt><tt class="py-name">models</tt> <tt class="py-keyword">import</tt> <tt class="py-name">Manager</tt> </tt>
<a name="L187"></a><tt class="py-lineno">187</tt>  <tt class="py-line">    <tt class="py-keyword">from</tt> <tt class="py-name">django</tt><tt class="py-op">.</tt><tt class="py-name">db</tt><tt class="py-op">.</tt><tt class="py-name">models</tt><tt class="py-op">.</tt><tt class="py-name">query</tt> <tt class="py-keyword">import</tt> <tt class="py-name">Q</tt><tt class="py-op">,</tt> <tt class="py-name">QuerySet</tt> </tt>
<a name="L188"></a><tt class="py-lineno">188</tt>  <tt class="py-line">    <tt class="py-keyword">if</tt> <tt id="link-1" class="py-name"><a title="qmanager.OLD_VERSION" class="py-name" href="#" onclick="return doclink('link-1', 'OLD_VERSION', 'link-0');">OLD_VERSION</a></tt><tt class="py-op">:</tt> </tt>
<a name="L189"></a><tt class="py-lineno">189</tt>  <tt class="py-line">        <tt class="py-keyword">from</tt> <tt class="py-name">django</tt><tt class="py-op">.</tt><tt class="py-name">db</tt><tt class="py-op">.</tt><tt class="py-name">models</tt><tt class="py-op">.</tt><tt class="py-name">query</tt> <tt class="py-keyword">import</tt> <tt class="py-name">QNot</tt><tt class="py-op">,</tt> <tt class="py-name">QOperator</tt> </tt>
<a name="L190"></a><tt class="py-lineno">190</tt>  <tt class="py-line"><tt class="py-keyword">except</tt> <tt class="py-op">(</tt><tt class="py-name">EnvironmentError</tt><tt class="py-op">,</tt> <tt class="py-name">ImportError</tt><tt class="py-op">)</tt><tt class="py-op">,</tt> <tt id="link-2" class="py-name" targets="Variable qmanager.exc=qmanager-module.html#exc"><a title="qmanager.exc" class="py-name" href="#" onclick="return doclink('link-2', 'exc', 'link-2');">exc</a></tt><tt class="py-op">:</tt> </tt>
<a name="L191"></a><tt class="py-lineno">191</tt>  <tt class="py-line">    <tt class="py-keyword">if</tt> <tt id="link-3" class="py-name"><a title="qmanager.OLD_VERSION" class="py-name" href="#" onclick="return doclink('link-3', 'OLD_VERSION', 'link-0');">OLD_VERSION</a></tt><tt class="py-op">:</tt> </tt>
<a name="L192"></a><tt class="py-lineno">192</tt>  <tt class="py-line">        <tt class="py-name">Manager</tt><tt class="py-op">,</tt> <tt class="py-name">Q</tt><tt class="py-op">,</tt> <tt class="py-name">QuerySet</tt><tt class="py-op">,</tt> <tt class="py-name">QNot</tt><tt class="py-op">,</tt> <tt class="py-name">QOperator</tt> <tt class="py-op">=</tt> <tt class="py-op">(</tt><tt class="py-name">object</tt><tt class="py-op">,</tt><tt class="py-op">)</tt> <tt class="py-op">*</tt> <tt class="py-number">5</tt> </tt>
<a name="L193"></a><tt class="py-lineno">193</tt>  <tt class="py-line">        <tt id="link-4" class="py-name" targets="Variable qmanager.MISSING_CLASSES=qmanager-module.html#MISSING_CLASSES"><a title="qmanager.MISSING_CLASSES" class="py-name" href="#" onclick="return doclink('link-4', 'MISSING_CLASSES', 'link-4');">MISSING_CLASSES</a></tt> <tt class="py-op">=</tt> <tt class="py-string">'Manager, Q, QuerySet, QNot and QOperator'</tt> </tt>
<a name="L194"></a><tt class="py-lineno">194</tt>  <tt class="py-line">    <tt class="py-keyword">else</tt><tt class="py-op">:</tt> </tt>
<a name="L195"></a><tt class="py-lineno">195</tt>  <tt class="py-line">        <tt class="py-name">Manager</tt><tt class="py-op">,</tt> <tt class="py-name">Q</tt><tt class="py-op">,</tt> <tt class="py-name">QuerySet</tt> <tt class="py-op">=</tt> <tt class="py-op">(</tt><tt class="py-name">object</tt><tt class="py-op">,</tt><tt class="py-op">)</tt> <tt class="py-op">*</tt> <tt class="py-number">3</tt> </tt>
<a name="L196"></a><tt class="py-lineno">196</tt>  <tt class="py-line">        <tt id="link-5" class="py-name"><a title="qmanager.MISSING_CLASSES" class="py-name" href="#" onclick="return doclink('link-5', 'MISSING_CLASSES', 'link-4');">MISSING_CLASSES</a></tt> <tt class="py-op">=</tt> <tt class="py-string">'Manager, Q and QuerySet'</tt> </tt>
<a name="L197"></a><tt class="py-lineno">197</tt>  <tt class="py-line">    <tt class="py-keyword">print</tt> <tt class="py-string">"""\</tt> </tt>
<a name="L198"></a><tt class="py-lineno">198</tt>  <tt class="py-line"><tt class="py-string">Warning: Using dummy classes for %s.</tt> </tt>
<a name="L199"></a><tt class="py-lineno">199</tt>  <tt class="py-line"><tt class="py-string">Nothing will work correctly; however, you can still view docstrings and</tt> </tt>
<a name="L200"></a><tt class="py-lineno">200</tt>  <tt class="py-line"><tt class="py-string">information on class and function names (handy when at the interpreter).</tt> </tt>
<a name="L201"></a><tt class="py-lineno">201</tt>  <tt class="py-line"><tt class="py-string">The exception raised was:</tt> </tt>
<a name="L202"></a><tt class="py-lineno">202</tt>  <tt class="py-line"><tt class="py-string">    %s: %s"""</tt> <tt class="py-op">%</tt> <tt class="py-op">(</tt><tt id="link-6" class="py-name"><a title="qmanager.MISSING_CLASSES" class="py-name" href="#" onclick="return doclink('link-6', 'MISSING_CLASSES', 'link-4');">MISSING_CLASSES</a></tt><tt class="py-op">,</tt> <tt id="link-7" class="py-name"><a title="qmanager.exc" class="py-name" href="#" onclick="return doclink('link-7', 'exc', 'link-2');">exc</a></tt><tt class="py-op">.</tt><tt class="py-name">__class__</tt><tt class="py-op">.</tt><tt class="py-name">__name__</tt><tt class="py-op">,</tt> <tt id="link-8" class="py-name"><a title="qmanager.exc" class="py-name" href="#" onclick="return doclink('link-8', 'exc', 'link-2');">exc</a></tt><tt class="py-op">.</tt><tt class="py-name">message</tt><tt class="py-op">)</tt> </tt>
<a name="L203"></a><tt class="py-lineno">203</tt>  <tt class="py-line"> </tt>
<a name="QManager"></a><div id="QManager-def"><a name="L204"></a><tt class="py-lineno">204</tt> <a class="py-toggle" href="#" id="QManager-toggle" onclick="return toggle('QManager');">-</a><tt class="py-line"><tt class="py-keyword">class</tt> <a class="py-def-name" href="qmanager.QManager-class.html">QManager</a><tt class="py-op">(</tt><tt class="py-base-class">Manager</tt><tt class="py-op">)</tt><tt class="py-op">:</tt> </tt>
</div><div id="QManager-collapsed" style="display:none;" pad="+++" indent="++++"></div><div id="QManager-expanded"><a name="L205"></a><tt class="py-lineno">205</tt>  <tt class="py-line">     </tt>
<a name="L206"></a><tt class="py-lineno">206</tt>  <tt class="py-line">    <tt class="py-docstring">"""</tt> </tt>
<a name="L207"></a><tt class="py-lineno">207</tt>  <tt class="py-line"><tt class="py-docstring">    Boilerplate Django manager which filters via a custom query.</tt> </tt>
<a name="L208"></a><tt class="py-lineno">208</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L209"></a><tt class="py-lineno">209</tt>  <tt class="py-line"><tt class="py-docstring">    Introduction</tt> </tt>
<a name="L210"></a><tt class="py-lineno">210</tt>  <tt class="py-line"><tt class="py-docstring">    ============</tt> </tt>
<a name="L211"></a><tt class="py-lineno">211</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L212"></a><tt class="py-lineno">212</tt>  <tt class="py-line"><tt class="py-docstring">    The ``QManager`` class is a subclass of ``django.db.models.Manager``, which</tt> </tt>
<a name="L213"></a><tt class="py-lineno">213</tt>  <tt class="py-line"><tt class="py-docstring">    defines several custom methods and attributes, and overrides several</tt> </tt>
<a name="L214"></a><tt class="py-lineno">214</tt>  <tt class="py-line"><tt class="py-docstring">    others. For more information on usage, consult the module-level</tt> </tt>
<a name="L215"></a><tt class="py-lineno">215</tt>  <tt class="py-line"><tt class="py-docstring">    documentation.</tt> </tt>
<a name="L216"></a><tt class="py-lineno">216</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L217"></a><tt class="py-lineno">217</tt>  <tt class="py-line"><tt class="py-docstring">    Overridden Methods</tt> </tt>
<a name="L218"></a><tt class="py-lineno">218</tt>  <tt class="py-line"><tt class="py-docstring">    ==================</tt> </tt>
<a name="L219"></a><tt class="py-lineno">219</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L220"></a><tt class="py-lineno">220</tt>  <tt class="py-line"><tt class="py-docstring">        *   ``__init__``</tt> </tt>
<a name="L221"></a><tt class="py-lineno">221</tt>  <tt class="py-line"><tt class="py-docstring">            Initialize a ``QManager`` instance, with an optional query.</tt> </tt>
<a name="L222"></a><tt class="py-lineno">222</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L223"></a><tt class="py-lineno">223</tt>  <tt class="py-line"><tt class="py-docstring">        *   ``__setattr__``</tt> </tt>
<a name="L224"></a><tt class="py-lineno">224</tt>  <tt class="py-line"><tt class="py-docstring">            Set an attribute on a ``QManager`` to a certain value, with extras.</tt> </tt>
<a name="L225"></a><tt class="py-lineno">225</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L226"></a><tt class="py-lineno">226</tt>  <tt class="py-line"><tt class="py-docstring">        *   ``get_query_set``</tt> </tt>
<a name="L227"></a><tt class="py-lineno">227</tt>  <tt class="py-line"><tt class="py-docstring">            Return the query set for a ``QManager`` instance's query.</tt> </tt>
<a name="L228"></a><tt class="py-lineno">228</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L229"></a><tt class="py-lineno">229</tt>  <tt class="py-line"><tt class="py-docstring">    New Methods</tt> </tt>
<a name="L230"></a><tt class="py-lineno">230</tt>  <tt class="py-line"><tt class="py-docstring">    ===========</tt> </tt>
<a name="L231"></a><tt class="py-lineno">231</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L232"></a><tt class="py-lineno">232</tt>  <tt class="py-line"><tt class="py-docstring">        *   ``__invert__``</tt> </tt>
<a name="L233"></a><tt class="py-lineno">233</tt>  <tt class="py-line"><tt class="py-docstring">            Return the complementary query of this ``QManager`` instance.</tt> </tt>
<a name="L234"></a><tt class="py-lineno">234</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L235"></a><tt class="py-lineno">235</tt>  <tt class="py-line"><tt class="py-docstring">        *   ``__and__``</tt> </tt>
<a name="L236"></a><tt class="py-lineno">236</tt>  <tt class="py-line"><tt class="py-docstring">            Return the logical 'and' of a ``QManager`` with another query.</tt> </tt>
<a name="L237"></a><tt class="py-lineno">237</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L238"></a><tt class="py-lineno">238</tt>  <tt class="py-line"><tt class="py-docstring">        *   ``__or__``</tt> </tt>
<a name="L239"></a><tt class="py-lineno">239</tt>  <tt class="py-line"><tt class="py-docstring">            Return the logical 'or' of a ``QManager`` with another query.</tt> </tt>
<a name="L240"></a><tt class="py-lineno">240</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L241"></a><tt class="py-lineno">241</tt>  <tt class="py-line"><tt class="py-docstring">        *   ``__xor__``</tt> </tt>
<a name="L242"></a><tt class="py-lineno">242</tt>  <tt class="py-line"><tt class="py-docstring">            Return the logical 'xor' of a ``QManager`` with another query.</tt> </tt>
<a name="L243"></a><tt class="py-lineno">243</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L244"></a><tt class="py-lineno">244</tt>  <tt class="py-line"><tt class="py-docstring">        *   ``__rand__``</tt> </tt>
<a name="L245"></a><tt class="py-lineno">245</tt>  <tt class="py-line"><tt class="py-docstring">            Same as ``__and__``, but works in reverse.</tt> </tt>
<a name="L246"></a><tt class="py-lineno">246</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L247"></a><tt class="py-lineno">247</tt>  <tt class="py-line"><tt class="py-docstring">        *   ``__ror__``</tt> </tt>
<a name="L248"></a><tt class="py-lineno">248</tt>  <tt class="py-line"><tt class="py-docstring">            Same as ``__or__``, but works in reverse.</tt> </tt>
<a name="L249"></a><tt class="py-lineno">249</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L250"></a><tt class="py-lineno">250</tt>  <tt class="py-line"><tt class="py-docstring">        *   ``__rxor__``</tt> </tt>
<a name="L251"></a><tt class="py-lineno">251</tt>  <tt class="py-line"><tt class="py-docstring">            Same as ``__xor__``, but works in reverse.</tt> </tt>
<a name="L252"></a><tt class="py-lineno">252</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L253"></a><tt class="py-lineno">253</tt>  <tt class="py-line"><tt class="py-docstring">    Consult the respective documentation for a method for more information on</tt> </tt>
<a name="L254"></a><tt class="py-lineno">254</tt>  <tt class="py-line"><tt class="py-docstring">    that method's usage and behaviour.</tt> </tt>
<a name="L255"></a><tt class="py-lineno">255</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L256"></a><tt class="py-lineno">256</tt>  <tt class="py-line"><tt class="py-docstring">    The ``query`` Attribute</tt> </tt>
<a name="L257"></a><tt class="py-lineno">257</tt>  <tt class="py-line"><tt class="py-docstring">    =======================</tt> </tt>
<a name="L258"></a><tt class="py-lineno">258</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L259"></a><tt class="py-lineno">259</tt>  <tt class="py-line"><tt class="py-docstring">    A ``QManager`` instance has one additional attribute called ``query`` which</tt> </tt>
<a name="L260"></a><tt class="py-lineno">260</tt>  <tt class="py-line"><tt class="py-docstring">    holds a ``Q`` instance - the representation of a database query in Django's</tt> </tt>
<a name="L261"></a><tt class="py-lineno">261</tt>  <tt class="py-line"><tt class="py-docstring">    ORM. The ``Q`` class is found in ``django.db.models.query``, and is itself</tt> </tt>
<a name="L262"></a><tt class="py-lineno">262</tt>  <tt class="py-line"><tt class="py-docstring">    a subclass of ``django.utils.tree.Node``.</tt> </tt>
<a name="L263"></a><tt class="py-lineno">263</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L264"></a><tt class="py-lineno">264</tt>  <tt class="py-line"><tt class="py-docstring">    For more information on query objects, consult the official documentation</tt> </tt>
<a name="L265"></a><tt class="py-lineno">265</tt>  <tt class="py-line"><tt class="py-docstring">    for Django's database API (this is included in the Django source).</tt> </tt>
<a name="L266"></a><tt class="py-lineno">266</tt>  <tt class="py-line"><tt class="py-docstring">    """</tt> </tt>
<a name="L267"></a><tt class="py-lineno">267</tt>  <tt class="py-line">     </tt>
<a name="QManager.__init__"></a><div id="QManager.__init__-def"><a name="L268"></a><tt class="py-lineno">268</tt> <a class="py-toggle" href="#" id="QManager.__init__-toggle" onclick="return toggle('QManager.__init__');">-</a><tt class="py-line">    <tt class="py-keyword">def</tt> <a class="py-def-name" href="qmanager.QManager-class.html#__init__">__init__</a><tt class="py-op">(</tt><tt class="py-param">self</tt><tt class="py-op">,</tt> <tt class="py-param">query</tt><tt class="py-op">=</tt><tt class="py-name">None</tt><tt class="py-op">)</tt><tt class="py-op">:</tt> </tt>
</div><div id="QManager.__init__-collapsed" style="display:none;" pad="+++" indent="++++++++"></div><div id="QManager.__init__-expanded"><a name="L269"></a><tt class="py-lineno">269</tt>  <tt class="py-line">        <tt class="py-docstring">"""</tt> </tt>
<a name="L270"></a><tt class="py-lineno">270</tt>  <tt class="py-line"><tt class="py-docstring">        Initialize a ``QManager`` instance, with an optional query.</tt> </tt>
<a name="L271"></a><tt class="py-lineno">271</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L272"></a><tt class="py-lineno">272</tt>  <tt class="py-line"><tt class="py-docstring">        The ``__init__`` method intializes a ``QManager`` instance, giving it a</tt> </tt>
<a name="L273"></a><tt class="py-lineno">273</tt>  <tt class="py-line"><tt class="py-docstring">        query by trying three things (in this order):</tt> </tt>
<a name="L274"></a><tt class="py-lineno">274</tt>  <tt class="py-line"><tt class="py-docstring">            </tt> </tt>
<a name="L275"></a><tt class="py-lineno">275</tt>  <tt class="py-line"><tt class="py-docstring">            1.  Arguments passed to ``__init__`` are turned into ``Q``</tt> </tt>
<a name="L276"></a><tt class="py-lineno">276</tt>  <tt class="py-line"><tt class="py-docstring">                instances by the ``get_valid_query`` function in this module</tt> </tt>
<a name="L277"></a><tt class="py-lineno">277</tt>  <tt class="py-line"><tt class="py-docstring">                (consult docstring for more information).</tt> </tt>
<a name="L278"></a><tt class="py-lineno">278</tt>  <tt class="py-line"><tt class="py-docstring">                </tt> </tt>
<a name="L279"></a><tt class="py-lineno">279</tt>  <tt class="py-line"><tt class="py-docstring">            2.  A ``query`` attribute specified on the class itself. This may</tt> </tt>
<a name="L280"></a><tt class="py-lineno">280</tt>  <tt class="py-line"><tt class="py-docstring">                be present due to subclassing (see docstring for the</tt> </tt>
<a name="L281"></a><tt class="py-lineno">281</tt>  <tt class="py-line"><tt class="py-docstring">                ``QManagerFactory()`` function in this module).</tt> </tt>
<a name="L282"></a><tt class="py-lineno">282</tt>  <tt class="py-line"><tt class="py-docstring">                </tt> </tt>
<a name="L283"></a><tt class="py-lineno">283</tt>  <tt class="py-line"><tt class="py-docstring">            3.  An empty ``Q`` instance (given by initializing ``Q`` with no</tt> </tt>
<a name="L284"></a><tt class="py-lineno">284</tt>  <tt class="py-line"><tt class="py-docstring">                arguments).</tt> </tt>
<a name="L285"></a><tt class="py-lineno">285</tt>  <tt class="py-line"><tt class="py-docstring">            </tt> </tt>
<a name="L286"></a><tt class="py-lineno">286</tt>  <tt class="py-line"><tt class="py-docstring">        It then calls the ``Manager`` class's default ``__init__`` method on</tt> </tt>
<a name="L287"></a><tt class="py-lineno">287</tt>  <tt class="py-line"><tt class="py-docstring">        the instance.</tt> </tt>
<a name="L288"></a><tt class="py-lineno">288</tt>  <tt class="py-line"><tt class="py-docstring">        """</tt> </tt>
<a name="L289"></a><tt class="py-lineno">289</tt>  <tt class="py-line">        <tt class="py-keyword">if</tt> <tt class="py-name">query</tt><tt class="py-op">:</tt> </tt>
<a name="L290"></a><tt class="py-lineno">290</tt>  <tt class="py-line">            <tt class="py-name">self</tt><tt class="py-op">.</tt><tt class="py-name">query</tt> <tt class="py-op">=</tt> <tt id="link-9" class="py-name" targets="Function qmanager.get_valid_query()=qmanager-module.html#get_valid_query"><a title="qmanager.get_valid_query" class="py-name" href="#" onclick="return doclink('link-9', 'get_valid_query', 'link-9');">get_valid_query</a></tt><tt class="py-op">(</tt><tt class="py-name">query</tt><tt class="py-op">)</tt> </tt>
<a name="L291"></a><tt class="py-lineno">291</tt>  <tt class="py-line">        <tt class="py-keyword">elif</tt> <tt class="py-name">hasattr</tt><tt class="py-op">(</tt><tt class="py-name">self</tt><tt class="py-op">,</tt> <tt class="py-string">'query'</tt><tt class="py-op">)</tt><tt class="py-op">:</tt> </tt>
<a name="L292"></a><tt class="py-lineno">292</tt>  <tt class="py-line">            <tt class="py-name">self</tt><tt class="py-op">.</tt><tt class="py-name">query</tt> <tt class="py-op">=</tt> <tt id="link-10" class="py-name"><a title="qmanager.get_valid_query" class="py-name" href="#" onclick="return doclink('link-10', 'get_valid_query', 'link-9');">get_valid_query</a></tt><tt class="py-op">(</tt><tt class="py-name">self</tt><tt class="py-op">.</tt><tt class="py-name">query</tt><tt class="py-op">)</tt> </tt>
<a name="L293"></a><tt class="py-lineno">293</tt>  <tt class="py-line">        <tt class="py-keyword">else</tt><tt class="py-op">:</tt> </tt>
<a name="L294"></a><tt class="py-lineno">294</tt>  <tt class="py-line">            <tt class="py-name">self</tt><tt class="py-op">.</tt><tt class="py-name">query</tt> <tt class="py-op">=</tt> <tt class="py-name">Q</tt><tt class="py-op">(</tt><tt class="py-op">)</tt> </tt>
<a name="L295"></a><tt class="py-lineno">295</tt>  <tt class="py-line">        <tt class="py-name">super</tt><tt class="py-op">(</tt><tt id="link-11" class="py-name" targets="Class qmanager.QManager=qmanager.QManager-class.html"><a title="qmanager.QManager" class="py-name" href="#" onclick="return doclink('link-11', 'QManager', 'link-11');">QManager</a></tt><tt class="py-op">,</tt> <tt class="py-name">self</tt><tt class="py-op">)</tt><tt class="py-op">.</tt><tt id="link-12" class="py-name" targets="Method qmanager.QManager.__init__()=qmanager.QManager-class.html#__init__"><a title="qmanager.QManager.__init__" class="py-name" href="#" onclick="return doclink('link-12', '__init__', 'link-12');">__init__</a></tt><tt class="py-op">(</tt><tt class="py-op">)</tt> </tt>
</div><a name="L296"></a><tt class="py-lineno">296</tt>  <tt class="py-line">     </tt>
<a name="QManager.__invert__"></a><div id="QManager.__invert__-def"><a name="L297"></a><tt class="py-lineno">297</tt> <a class="py-toggle" href="#" id="QManager.__invert__-toggle" onclick="return toggle('QManager.__invert__');">-</a><tt class="py-line">    <tt class="py-keyword">def</tt> <a class="py-def-name" href="qmanager.QManager-class.html#__invert__">__invert__</a><tt class="py-op">(</tt><tt class="py-param">self</tt><tt class="py-op">)</tt><tt class="py-op">:</tt> </tt>
</div><div id="QManager.__invert__-collapsed" style="display:none;" pad="+++" indent="++++++++"></div><div id="QManager.__invert__-expanded"><a name="L298"></a><tt class="py-lineno">298</tt>  <tt class="py-line">        <tt class="py-docstring">"""</tt> </tt>
<a name="L299"></a><tt class="py-lineno">299</tt>  <tt class="py-line"><tt class="py-docstring">        Return the complementary query of this ``QManager`` instance.</tt> </tt>
<a name="L300"></a><tt class="py-lineno">300</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L301"></a><tt class="py-lineno">301</tt>  <tt class="py-line"><tt class="py-docstring">        ``__invert__`` provides a shortcut for finding the complement of a</tt> </tt>
<a name="L302"></a><tt class="py-lineno">302</tt>  <tt class="py-line"><tt class="py-docstring">        query set by returning a new ``QManager`` instance in which ``QNot``</tt> </tt>
<a name="L303"></a><tt class="py-lineno">303</tt>  <tt class="py-line"><tt class="py-docstring">        has been initialized on the query. Filtering by a ``QNot`` instance (a</tt> </tt>
<a name="L304"></a><tt class="py-lineno">304</tt>  <tt class="py-line"><tt class="py-docstring">        subclass of ``Q``) is the same as excluding by the original ``Q``, thus</tt> </tt>
<a name="L305"></a><tt class="py-lineno">305</tt>  <tt class="py-line"><tt class="py-docstring">        allowing ``QManager`` instances to be complemented.</tt> </tt>
<a name="L306"></a><tt class="py-lineno">306</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L307"></a><tt class="py-lineno">307</tt>  <tt class="py-line"><tt class="py-docstring">        By defining this as ``__invert__``, it allows the shortcut of</tt> </tt>
<a name="L308"></a><tt class="py-lineno">308</tt>  <tt class="py-line"><tt class="py-docstring">        ``~manager_name`` to be used instead of calling, for example,</tt> </tt>
<a name="L309"></a><tt class="py-lineno">309</tt>  <tt class="py-line"><tt class="py-docstring">        ``manager_name.not_()``.</tt> </tt>
<a name="L310"></a><tt class="py-lineno">310</tt>  <tt class="py-line"><tt class="py-docstring">        """</tt> </tt>
<a name="L311"></a><tt class="py-lineno">311</tt>  <tt class="py-line">        <tt class="py-keyword">if</tt> <tt id="link-13" class="py-name"><a title="qmanager.OLD_VERSION" class="py-name" href="#" onclick="return doclink('link-13', 'OLD_VERSION', 'link-0');">OLD_VERSION</a></tt><tt class="py-op">:</tt> </tt>
<a name="L312"></a><tt class="py-lineno">312</tt>  <tt class="py-line">            <tt class="py-keyword">return</tt> <tt class="py-name">self</tt><tt class="py-op">.</tt><tt class="py-name">__class__</tt><tt class="py-op">(</tt><tt class="py-name">QNot</tt><tt class="py-op">(</tt><tt class="py-name">self</tt><tt class="py-op">.</tt><tt class="py-name">query</tt><tt class="py-op">)</tt><tt class="py-op">)</tt> </tt>
<a name="L313"></a><tt class="py-lineno">313</tt>  <tt class="py-line">        <tt class="py-keyword">return</tt> <tt class="py-name">self</tt><tt class="py-op">.</tt><tt class="py-name">__class__</tt><tt class="py-op">(</tt><tt class="py-op">~</tt><tt class="py-name">self</tt><tt class="py-op">.</tt><tt class="py-name">query</tt><tt class="py-op">)</tt> </tt>
</div><a name="L314"></a><tt class="py-lineno">314</tt>  <tt class="py-line">     </tt>
<a name="QManager.__and__"></a><div id="QManager.__and__-def"><a name="L315"></a><tt class="py-lineno">315</tt> <a class="py-toggle" href="#" id="QManager.__and__-toggle" onclick="return toggle('QManager.__and__');">-</a><tt class="py-line">    <tt class="py-keyword">def</tt> <a class="py-def-name" href="qmanager.QManager-class.html#__and__">__and__</a><tt class="py-op">(</tt><tt class="py-param">self</tt><tt class="py-op">,</tt> <tt class="py-param">query</tt><tt class="py-op">)</tt><tt class="py-op">:</tt> </tt>
</div><div id="QManager.__and__-collapsed" style="display:none;" pad="+++" indent="++++++++"></div><div id="QManager.__and__-expanded"><a name="L316"></a><tt class="py-lineno">316</tt>  <tt class="py-line">        <tt class="py-docstring">"""</tt> </tt>
<a name="L317"></a><tt class="py-lineno">317</tt>  <tt class="py-line"><tt class="py-docstring">        Return the logical 'and' of this ``QManager`` with another query.</tt> </tt>
<a name="L318"></a><tt class="py-lineno">318</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L319"></a><tt class="py-lineno">319</tt>  <tt class="py-line"><tt class="py-docstring">        ``__and__`` allows the combination of this instance's query with</tt> </tt>
<a name="L320"></a><tt class="py-lineno">320</tt>  <tt class="py-line"><tt class="py-docstring">        another query via the 'and' logical operator. ``Q`` objects support</tt> </tt>
<a name="L321"></a><tt class="py-lineno">321</tt>  <tt class="py-line"><tt class="py-docstring">        this inherently, so all that needs to be done is for a new ``QManager``</tt> </tt>
<a name="L322"></a><tt class="py-lineno">322</tt>  <tt class="py-line"><tt class="py-docstring">        instance to be created using the ``&amp;`` of the instance's query and the</tt> </tt>
<a name="L323"></a><tt class="py-lineno">323</tt>  <tt class="py-line"><tt class="py-docstring">        argument query.</tt> </tt>
<a name="L324"></a><tt class="py-lineno">324</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L325"></a><tt class="py-lineno">325</tt>  <tt class="py-line"><tt class="py-docstring">        In order to allow objects of all sorts to be and'd onto a ``QManager``</tt> </tt>
<a name="L326"></a><tt class="py-lineno">326</tt>  <tt class="py-line"><tt class="py-docstring">        instance, ``get_valid_query`` is called on the argument. This does not</tt> </tt>
<a name="L327"></a><tt class="py-lineno">327</tt>  <tt class="py-line"><tt class="py-docstring">        modify the original argument.</tt> </tt>
<a name="L328"></a><tt class="py-lineno">328</tt>  <tt class="py-line"><tt class="py-docstring">        """</tt> </tt>
<a name="L329"></a><tt class="py-lineno">329</tt>  <tt class="py-line">        <tt class="py-keyword">return</tt> <tt class="py-name">self</tt><tt class="py-op">.</tt><tt class="py-name">__class__</tt><tt class="py-op">(</tt><tt class="py-name">self</tt><tt class="py-op">.</tt><tt class="py-name">query</tt> <tt class="py-op">&amp;</tt> <tt id="link-14" class="py-name"><a title="qmanager.get_valid_query" class="py-name" href="#" onclick="return doclink('link-14', 'get_valid_query', 'link-9');">get_valid_query</a></tt><tt class="py-op">(</tt><tt class="py-name">query</tt><tt class="py-op">)</tt><tt class="py-op">)</tt> </tt>
</div><a name="L330"></a><tt class="py-lineno">330</tt>  <tt class="py-line">     </tt>
<a name="QManager.__or__"></a><div id="QManager.__or__-def"><a name="L331"></a><tt class="py-lineno">331</tt> <a class="py-toggle" href="#" id="QManager.__or__-toggle" onclick="return toggle('QManager.__or__');">-</a><tt class="py-line">    <tt class="py-keyword">def</tt> <a class="py-def-name" href="qmanager.QManager-class.html#__or__">__or__</a><tt class="py-op">(</tt><tt class="py-param">self</tt><tt class="py-op">,</tt> <tt class="py-param">query</tt><tt class="py-op">)</tt><tt class="py-op">:</tt> </tt>
</div><div id="QManager.__or__-collapsed" style="display:none;" pad="+++" indent="++++++++"></div><div id="QManager.__or__-expanded"><a name="L332"></a><tt class="py-lineno">332</tt>  <tt class="py-line">        <tt class="py-docstring">"""</tt> </tt>
<a name="L333"></a><tt class="py-lineno">333</tt>  <tt class="py-line"><tt class="py-docstring">        Return the logical 'or' of this ``QManager`` with another query.</tt> </tt>
<a name="L334"></a><tt class="py-lineno">334</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L335"></a><tt class="py-lineno">335</tt>  <tt class="py-line"><tt class="py-docstring">        ``__or__`` allows the combination of this instance's query with</tt> </tt>
<a name="L336"></a><tt class="py-lineno">336</tt>  <tt class="py-line"><tt class="py-docstring">        another query via the 'or' logical operator. ``Q`` objects support this</tt> </tt>
<a name="L337"></a><tt class="py-lineno">337</tt>  <tt class="py-line"><tt class="py-docstring">        inherently, so all that needs to be done is for a new ``QManager``</tt> </tt>
<a name="L338"></a><tt class="py-lineno">338</tt>  <tt class="py-line"><tt class="py-docstring">        instance to be created using the ``|`` of the instance's query and the</tt> </tt>
<a name="L339"></a><tt class="py-lineno">339</tt>  <tt class="py-line"><tt class="py-docstring">        argument query.</tt> </tt>
<a name="L340"></a><tt class="py-lineno">340</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L341"></a><tt class="py-lineno">341</tt>  <tt class="py-line"><tt class="py-docstring">        In order to allow objects of all sorts to be or'd onto a ``QManager``</tt> </tt>
<a name="L342"></a><tt class="py-lineno">342</tt>  <tt class="py-line"><tt class="py-docstring">        instance, ``get_valid_query`` is called on the argument. This does not</tt> </tt>
<a name="L343"></a><tt class="py-lineno">343</tt>  <tt class="py-line"><tt class="py-docstring">        modify the original argument.</tt> </tt>
<a name="L344"></a><tt class="py-lineno">344</tt>  <tt class="py-line"><tt class="py-docstring">        """</tt> </tt>
<a name="L345"></a><tt class="py-lineno">345</tt>  <tt class="py-line">        <tt class="py-keyword">return</tt> <tt class="py-name">self</tt><tt class="py-op">.</tt><tt class="py-name">__class__</tt><tt class="py-op">(</tt><tt class="py-name">self</tt><tt class="py-op">.</tt><tt class="py-name">query</tt> <tt class="py-op">|</tt> <tt id="link-15" class="py-name"><a title="qmanager.get_valid_query" class="py-name" href="#" onclick="return doclink('link-15', 'get_valid_query', 'link-9');">get_valid_query</a></tt><tt class="py-op">(</tt><tt class="py-name">query</tt><tt class="py-op">)</tt><tt class="py-op">)</tt> </tt>
</div><a name="L346"></a><tt class="py-lineno">346</tt>  <tt class="py-line">     </tt>
<a name="QManager.__xor__"></a><div id="QManager.__xor__-def"><a name="L347"></a><tt class="py-lineno">347</tt> <a class="py-toggle" href="#" id="QManager.__xor__-toggle" onclick="return toggle('QManager.__xor__');">-</a><tt class="py-line">    <tt class="py-keyword">def</tt> <a class="py-def-name" href="qmanager.QManager-class.html#__xor__">__xor__</a><tt class="py-op">(</tt><tt class="py-param">self</tt><tt class="py-op">,</tt> <tt class="py-param">query</tt><tt class="py-op">)</tt><tt class="py-op">:</tt> </tt>
</div><div id="QManager.__xor__-collapsed" style="display:none;" pad="+++" indent="++++++++"></div><div id="QManager.__xor__-expanded"><a name="L348"></a><tt class="py-lineno">348</tt>  <tt class="py-line">        <tt class="py-docstring">"""</tt> </tt>
<a name="L349"></a><tt class="py-lineno">349</tt>  <tt class="py-line"><tt class="py-docstring">        Return the logical 'xor' of this ``QManager`` with another query.</tt> </tt>
<a name="L350"></a><tt class="py-lineno">350</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L351"></a><tt class="py-lineno">351</tt>  <tt class="py-line"><tt class="py-docstring">        ``__xor__`` allows the combination of this instance's query with</tt> </tt>
<a name="L352"></a><tt class="py-lineno">352</tt>  <tt class="py-line"><tt class="py-docstring">        another query via the 'xor' logical operator. ``Q`` objects support</tt> </tt>
<a name="L353"></a><tt class="py-lineno">353</tt>  <tt class="py-line"><tt class="py-docstring">        this inherently, so all that needs to be done is for a new ``QManager``</tt> </tt>
<a name="L354"></a><tt class="py-lineno">354</tt>  <tt class="py-line"><tt class="py-docstring">        instance to be created using the ``^`` of the instance's query and the</tt> </tt>
<a name="L355"></a><tt class="py-lineno">355</tt>  <tt class="py-line"><tt class="py-docstring">        argument query.</tt> </tt>
<a name="L356"></a><tt class="py-lineno">356</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L357"></a><tt class="py-lineno">357</tt>  <tt class="py-line"><tt class="py-docstring">        Definition and Implementation</tt> </tt>
<a name="L358"></a><tt class="py-lineno">358</tt>  <tt class="py-line"><tt class="py-docstring">        =============================</tt> </tt>
<a name="L359"></a><tt class="py-lineno">359</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L360"></a><tt class="py-lineno">360</tt>  <tt class="py-line"><tt class="py-docstring">        The definition of an XOR is that it returns the records which fit</tt> </tt>
<a name="L361"></a><tt class="py-lineno">361</tt>  <tt class="py-line"><tt class="py-docstring">        *either* one query or the other - but not *both*. In terms of set</tt> </tt>
<a name="L362"></a><tt class="py-lineno">362</tt>  <tt class="py-line"><tt class="py-docstring">        theory (with A and B representing the sets returned by both queries),</tt> </tt>
<a name="L363"></a><tt class="py-lineno">363</tt>  <tt class="py-line"><tt class="py-docstring">        the XOR of A and B is the intersection of the union of the complements</tt> </tt>
<a name="L364"></a><tt class="py-lineno">364</tt>  <tt class="py-line"><tt class="py-docstring">        of A with B, and the union of A with B. In terms of boolean logic, XOR</tt> </tt>
<a name="L365"></a><tt class="py-lineno">365</tt>  <tt class="py-line"><tt class="py-docstring">        is defined as the AND of the OR of NOT A with NOT B, and the OR of A</tt> </tt>
<a name="L366"></a><tt class="py-lineno">366</tt>  <tt class="py-line"><tt class="py-docstring">        and B. In Python code::</tt> </tt>
<a name="L367"></a><tt class="py-lineno">367</tt>  <tt class="py-line"><tt class="py-docstring">            </tt> </tt>
<a name="L368"></a><tt class="py-lineno">368</tt>  <tt class="py-line"><tt class="py-docstring">            def xor(a, b):</tt> </tt>
<a name="L369"></a><tt class="py-lineno">369</tt>  <tt class="py-line"><tt class="py-docstring">                return ((not a) or (not b)) and (a or b)</tt> </tt>
<a name="L370"></a><tt class="py-lineno">370</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L371"></a><tt class="py-lineno">371</tt>  <tt class="py-line"><tt class="py-docstring">        Consult the source code for more information on the implementation.</tt> </tt>
<a name="L372"></a><tt class="py-lineno">372</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L373"></a><tt class="py-lineno">373</tt>  <tt class="py-line"><tt class="py-docstring">        In order to allow objects of all sorts to be xor'd onto a ``QManager``</tt> </tt>
<a name="L374"></a><tt class="py-lineno">374</tt>  <tt class="py-line"><tt class="py-docstring">        instance, ``get_valid_query`` is called on the argument. This does not</tt> </tt>
<a name="L375"></a><tt class="py-lineno">375</tt>  <tt class="py-line"><tt class="py-docstring">        modify the original argument.</tt> </tt>
<a name="L376"></a><tt class="py-lineno">376</tt>  <tt class="py-line"><tt class="py-docstring">        """</tt> </tt>
<a name="L377"></a><tt class="py-lineno">377</tt>  <tt class="py-line">        <tt class="py-name">query</tt> <tt class="py-op">=</tt> <tt id="link-16" class="py-name"><a title="qmanager.get_valid_query" class="py-name" href="#" onclick="return doclink('link-16', 'get_valid_query', 'link-9');">get_valid_query</a></tt><tt class="py-op">(</tt><tt class="py-name">query</tt><tt class="py-op">)</tt> </tt>
<a name="L378"></a><tt class="py-lineno">378</tt>  <tt class="py-line">        <tt class="py-keyword">if</tt> <tt id="link-17" class="py-name"><a title="qmanager.OLD_VERSION" class="py-name" href="#" onclick="return doclink('link-17', 'OLD_VERSION', 'link-0');">OLD_VERSION</a></tt><tt class="py-op">:</tt> </tt>
<a name="L379"></a><tt class="py-lineno">379</tt>  <tt class="py-line">            <tt class="py-keyword">return</tt> <tt class="py-name">self</tt><tt class="py-op">.</tt><tt class="py-name">__class__</tt><tt class="py-op">(</tt> </tt>
<a name="L380"></a><tt class="py-lineno">380</tt>  <tt class="py-line">                <tt class="py-op">(</tt><tt class="py-name">QNot</tt><tt class="py-op">(</tt><tt class="py-name">self</tt><tt class="py-op">.</tt><tt class="py-name">query</tt><tt class="py-op">)</tt> <tt class="py-op">|</tt> <tt class="py-name">QNot</tt><tt class="py-op">(</tt><tt class="py-name">query</tt><tt class="py-op">)</tt><tt class="py-op">)</tt> <tt class="py-op">&amp;</tt> </tt>
<a name="L381"></a><tt class="py-lineno">381</tt>  <tt class="py-line">                <tt class="py-op">(</tt><tt class="py-name">self</tt><tt class="py-op">.</tt><tt class="py-name">query</tt> <tt class="py-op">|</tt> <tt class="py-name">query</tt><tt class="py-op">)</tt><tt class="py-op">)</tt> </tt>
<a name="L382"></a><tt class="py-lineno">382</tt>  <tt class="py-line">        <tt class="py-keyword">return</tt> <tt class="py-name">self</tt><tt class="py-op">.</tt><tt class="py-name">__class__</tt><tt class="py-op">(</tt><tt class="py-op">(</tt><tt class="py-op">~</tt><tt class="py-name">self</tt><tt class="py-op">.</tt><tt class="py-name">query</tt> <tt class="py-op">|</tt> <tt class="py-op">~</tt><tt class="py-name">query</tt><tt class="py-op">)</tt> <tt class="py-op">&amp;</tt> <tt class="py-op">(</tt><tt class="py-name">self</tt><tt class="py-op">.</tt><tt class="py-name">query</tt> <tt class="py-op">|</tt> <tt class="py-name">query</tt><tt class="py-op">)</tt><tt class="py-op">)</tt> </tt>
</div><a name="L383"></a><tt class="py-lineno">383</tt>  <tt class="py-line">     </tt>
<a name="QManager.__setattr__"></a><div id="QManager.__setattr__-def"><a name="L384"></a><tt class="py-lineno">384</tt> <a class="py-toggle" href="#" id="QManager.__setattr__-toggle" onclick="return toggle('QManager.__setattr__');">-</a><tt class="py-line">    <tt class="py-keyword">def</tt> <a class="py-def-name" href="qmanager.QManager-class.html#__setattr__">__setattr__</a><tt class="py-op">(</tt><tt class="py-param">self</tt><tt class="py-op">,</tt> <tt class="py-param">attr</tt><tt class="py-op">,</tt> <tt class="py-param">value</tt><tt class="py-op">)</tt><tt class="py-op">:</tt> </tt>
</div><div id="QManager.__setattr__-collapsed" style="display:none;" pad="+++" indent="++++++++"></div><div id="QManager.__setattr__-expanded"><a name="L385"></a><tt class="py-lineno">385</tt>  <tt class="py-line">        <tt class="py-docstring">"""</tt> </tt>
<a name="L386"></a><tt class="py-lineno">386</tt>  <tt class="py-line"><tt class="py-docstring">        Set an attribute on a ``QManager`` to a certain value, with extras.</tt> </tt>
<a name="L387"></a><tt class="py-lineno">387</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L388"></a><tt class="py-lineno">388</tt>  <tt class="py-line"><tt class="py-docstring">        This does not differ greatly from the regular ``__setattr__``, except</tt> </tt>
<a name="L389"></a><tt class="py-lineno">389</tt>  <tt class="py-line"><tt class="py-docstring">        that, if the ``query`` attribute is being modified, then</tt> </tt>
<a name="L390"></a><tt class="py-lineno">390</tt>  <tt class="py-line"><tt class="py-docstring">        ``get_valid_query`` is called on the value which it is being set to, to</tt> </tt>
<a name="L391"></a><tt class="py-lineno">391</tt>  <tt class="py-line"><tt class="py-docstring">        allow queries to be validated and to come from several different</tt> </tt>
<a name="L392"></a><tt class="py-lineno">392</tt>  <tt class="py-line"><tt class="py-docstring">        sources.</tt> </tt>
<a name="L393"></a><tt class="py-lineno">393</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L394"></a><tt class="py-lineno">394</tt>  <tt class="py-line"><tt class="py-docstring">        As always, it is a good idea to consult the source code, as well as the</tt> </tt>
<a name="L395"></a><tt class="py-lineno">395</tt>  <tt class="py-line"><tt class="py-docstring">        source and docstring for the ``get_valid_query`` function.</tt> </tt>
<a name="L396"></a><tt class="py-lineno">396</tt>  <tt class="py-line"><tt class="py-docstring">        """</tt> </tt>
<a name="L397"></a><tt class="py-lineno">397</tt>  <tt class="py-line">        <tt class="py-keyword">if</tt> <tt class="py-name">attr</tt> <tt class="py-op">==</tt> <tt class="py-string">'query'</tt><tt class="py-op">:</tt> </tt>
<a name="L398"></a><tt class="py-lineno">398</tt>  <tt class="py-line">            <tt class="py-keyword">return</tt> <tt class="py-name">super</tt><tt class="py-op">(</tt><tt id="link-18" class="py-name"><a title="qmanager.QManager" class="py-name" href="#" onclick="return doclink('link-18', 'QManager', 'link-11');">QManager</a></tt><tt class="py-op">,</tt> <tt class="py-name">self</tt><tt class="py-op">)</tt><tt class="py-op">.</tt><tt id="link-19" class="py-name" targets="Method qmanager.QManager.__setattr__()=qmanager.QManager-class.html#__setattr__"><a title="qmanager.QManager.__setattr__" class="py-name" href="#" onclick="return doclink('link-19', '__setattr__', 'link-19');">__setattr__</a></tt><tt class="py-op">(</tt> </tt>
<a name="L399"></a><tt class="py-lineno">399</tt>  <tt class="py-line">                <tt class="py-name">attr</tt><tt class="py-op">,</tt> <tt id="link-20" class="py-name"><a title="qmanager.get_valid_query" class="py-name" href="#" onclick="return doclink('link-20', 'get_valid_query', 'link-9');">get_valid_query</a></tt><tt class="py-op">(</tt><tt class="py-name">value</tt><tt class="py-op">)</tt><tt class="py-op">)</tt> </tt>
<a name="L400"></a><tt class="py-lineno">400</tt>  <tt class="py-line">        <tt class="py-keyword">return</tt> <tt class="py-name">super</tt><tt class="py-op">(</tt><tt id="link-21" class="py-name"><a title="qmanager.QManager" class="py-name" href="#" onclick="return doclink('link-21', 'QManager', 'link-11');">QManager</a></tt><tt class="py-op">,</tt> <tt class="py-name">self</tt><tt class="py-op">)</tt><tt class="py-op">.</tt><tt id="link-22" class="py-name"><a title="qmanager.QManager.__setattr__" class="py-name" href="#" onclick="return doclink('link-22', '__setattr__', 'link-19');">__setattr__</a></tt><tt class="py-op">(</tt><tt class="py-name">attr</tt><tt class="py-op">,</tt> <tt class="py-name">value</tt><tt class="py-op">)</tt> </tt>
</div><a name="L401"></a><tt class="py-lineno">401</tt>  <tt class="py-line">     </tt>
<a name="QManager.get_query_set"></a><div id="QManager.get_query_set-def"><a name="L402"></a><tt class="py-lineno">402</tt> <a class="py-toggle" href="#" id="QManager.get_query_set-toggle" onclick="return toggle('QManager.get_query_set');">-</a><tt class="py-line">    <tt class="py-keyword">def</tt> <a class="py-def-name" href="qmanager.QManager-class.html#get_query_set">get_query_set</a><tt class="py-op">(</tt><tt class="py-param">self</tt><tt class="py-op">)</tt><tt class="py-op">:</tt> </tt>
</div><div id="QManager.get_query_set-collapsed" style="display:none;" pad="+++" indent="++++++++"></div><div id="QManager.get_query_set-expanded"><a name="L403"></a><tt class="py-lineno">403</tt>  <tt class="py-line">        <tt class="py-docstring">"""</tt> </tt>
<a name="L404"></a><tt class="py-lineno">404</tt>  <tt class="py-line"><tt class="py-docstring">        Return the query set for this ``QManager`` instance's query.</tt> </tt>
<a name="L405"></a><tt class="py-lineno">405</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L406"></a><tt class="py-lineno">406</tt>  <tt class="py-line"><tt class="py-docstring">        The ``QManager`` class's ``get_query_set`` method is a simple line of</tt> </tt>
<a name="L407"></a><tt class="py-lineno">407</tt>  <tt class="py-line"><tt class="py-docstring">        code::</tt> </tt>
<a name="L408"></a><tt class="py-lineno">408</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L409"></a><tt class="py-lineno">409</tt>  <tt class="py-line"><tt class="py-docstring">            return super(QManager, self).get_query_set().filter(self.query)</tt> </tt>
<a name="L410"></a><tt class="py-lineno">410</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L411"></a><tt class="py-lineno">411</tt>  <tt class="py-line"><tt class="py-docstring">        What it essentially does is returns the basic ``Manager`` class's query</tt> </tt>
<a name="L412"></a><tt class="py-lineno">412</tt>  <tt class="py-line"><tt class="py-docstring">        set for a model (i.e. all of a model's records), filtered by the</tt> </tt>
<a name="L413"></a><tt class="py-lineno">413</tt>  <tt class="py-line"><tt class="py-docstring">        ``QManager`` instance's query. This forms the main part of the</tt> </tt>
<a name="L414"></a><tt class="py-lineno">414</tt>  <tt class="py-line"><tt class="py-docstring">        abstraction which ``QManager`` provides.</tt> </tt>
<a name="L415"></a><tt class="py-lineno">415</tt>  <tt class="py-line"><tt class="py-docstring">        """</tt> </tt>
<a name="L416"></a><tt class="py-lineno">416</tt>  <tt class="py-line">        <tt class="py-keyword">return</tt> <tt class="py-name">super</tt><tt class="py-op">(</tt><tt id="link-23" class="py-name"><a title="qmanager.QManager" class="py-name" href="#" onclick="return doclink('link-23', 'QManager', 'link-11');">QManager</a></tt><tt class="py-op">,</tt> <tt class="py-name">self</tt><tt class="py-op">)</tt><tt class="py-op">.</tt><tt id="link-24" class="py-name" targets="Method qmanager.QManager.get_query_set()=qmanager.QManager-class.html#get_query_set"><a title="qmanager.QManager.get_query_set" class="py-name" href="#" onclick="return doclink('link-24', 'get_query_set', 'link-24');">get_query_set</a></tt><tt class="py-op">(</tt><tt class="py-op">)</tt><tt class="py-op">.</tt><tt class="py-name">filter</tt><tt class="py-op">(</tt><tt class="py-name">self</tt><tt class="py-op">.</tt><tt class="py-name">query</tt><tt class="py-op">)</tt> </tt>
</div><a name="L417"></a><tt class="py-lineno">417</tt>  <tt class="py-line">     </tt>
<a name="L418"></a><tt class="py-lineno">418</tt>  <tt class="py-line">    <tt class="py-name">__rand__</tt> <tt class="py-op">=</tt> <tt id="link-25" class="py-name" targets="Method qmanager.QManager.__and__()=qmanager.QManager-class.html#__and__"><a title="qmanager.QManager.__and__" class="py-name" href="#" onclick="return doclink('link-25', '__and__', 'link-25');">__and__</a></tt> </tt>
<a name="L419"></a><tt class="py-lineno">419</tt>  <tt class="py-line">    <tt class="py-name">__ror__</tt> <tt class="py-op">=</tt> <tt id="link-26" class="py-name" targets="Method qmanager.QManager.__or__()=qmanager.QManager-class.html#__or__"><a title="qmanager.QManager.__or__" class="py-name" href="#" onclick="return doclink('link-26', '__or__', 'link-26');">__or__</a></tt> </tt>
<a name="L420"></a><tt class="py-lineno">420</tt>  <tt class="py-line">    <tt class="py-name">__rxor__</tt> <tt class="py-op">=</tt> <tt id="link-27" class="py-name" targets="Method qmanager.QManager.__xor__()=qmanager.QManager-class.html#__xor__"><a title="qmanager.QManager.__xor__" class="py-name" href="#" onclick="return doclink('link-27', '__xor__', 'link-27');">__xor__</a></tt> </tt>
</div><a name="L421"></a><tt class="py-lineno">421</tt>  <tt class="py-line"> </tt>
<a name="QManagerFactory"></a><div id="QManagerFactory-def"><a name="L422"></a><tt class="py-lineno">422</tt> <a class="py-toggle" href="#" id="QManagerFactory-toggle" onclick="return toggle('QManagerFactory');">-</a><tt class="py-line"><tt class="py-keyword">def</tt> <a class="py-def-name" href="qmanager-module.html#QManagerFactory">QManagerFactory</a><tt class="py-op">(</tt><tt class="py-param">query</tt><tt class="py-op">,</tt> <tt class="py-param">name</tt><tt class="py-op">=</tt><tt class="py-name">None</tt><tt class="py-op">)</tt><tt class="py-op">:</tt> </tt>
</div><div id="QManagerFactory-collapsed" style="display:none;" pad="+++" indent="++++"></div><div id="QManagerFactory-expanded"><a name="L423"></a><tt class="py-lineno">423</tt>  <tt class="py-line">    <tt class="py-docstring">"""</tt> </tt>
<a name="L424"></a><tt class="py-lineno">424</tt>  <tt class="py-line"><tt class="py-docstring">    Construct a ``QManager`` subclass with a pre-defined query.</tt> </tt>
<a name="L425"></a><tt class="py-lineno">425</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L426"></a><tt class="py-lineno">426</tt>  <tt class="py-line"><tt class="py-docstring">    Introduction</tt> </tt>
<a name="L427"></a><tt class="py-lineno">427</tt>  <tt class="py-line"><tt class="py-docstring">    ============</tt> </tt>
<a name="L428"></a><tt class="py-lineno">428</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L429"></a><tt class="py-lineno">429</tt>  <tt class="py-line"><tt class="py-docstring">    The ``QManagerFactory`` function returns a new class, subclassed from</tt> </tt>
<a name="L430"></a><tt class="py-lineno">430</tt>  <tt class="py-line"><tt class="py-docstring">    ``QManager``, which has its ``query`` attribute defined at a class-level,</tt> </tt>
<a name="L431"></a><tt class="py-lineno">431</tt>  <tt class="py-line"><tt class="py-docstring">    rather than having to be specified on each instance. This allows the new</tt> </tt>
<a name="L432"></a><tt class="py-lineno">432</tt>  <tt class="py-line"><tt class="py-docstring">    class to be instantiated, with no arguments, and return a ``QManager`` with</tt> </tt>
<a name="L433"></a><tt class="py-lineno">433</tt>  <tt class="py-line"><tt class="py-docstring">    the prescribed query. For more information on how it does this, consult the</tt> </tt>
<a name="L434"></a><tt class="py-lineno">434</tt>  <tt class="py-line"><tt class="py-docstring">    docstring and source for ``QManager.__init__``.</tt> </tt>
<a name="L435"></a><tt class="py-lineno">435</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L436"></a><tt class="py-lineno">436</tt>  <tt class="py-line"><tt class="py-docstring">    A ``name`` keyword argument may also be specified, which will be used as</tt> </tt>
<a name="L437"></a><tt class="py-lineno">437</tt>  <tt class="py-line"><tt class="py-docstring">    the name of the returned class (by setting the class's ``__name__``</tt> </tt>
<a name="L438"></a><tt class="py-lineno">438</tt>  <tt class="py-line"><tt class="py-docstring">    attribute to this value).</tt> </tt>
<a name="L439"></a><tt class="py-lineno">439</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L440"></a><tt class="py-lineno">440</tt>  <tt class="py-line"><tt class="py-docstring">    Usage</tt> </tt>
<a name="L441"></a><tt class="py-lineno">441</tt>  <tt class="py-line"><tt class="py-docstring">    =====</tt> </tt>
<a name="L442"></a><tt class="py-lineno">442</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L443"></a><tt class="py-lineno">443</tt>  <tt class="py-line"><tt class="py-docstring">    This function is useful in cases where a query is needed across several</tt> </tt>
<a name="L444"></a><tt class="py-lineno">444</tt>  <tt class="py-line"><tt class="py-docstring">    model definitions, such as when several slightly different models share a</tt> </tt>
<a name="L445"></a><tt class="py-lineno">445</tt>  <tt class="py-line"><tt class="py-docstring">    common field, or set of fields, which would benefit from having some</tt> </tt>
<a name="L446"></a><tt class="py-lineno">446</tt>  <tt class="py-line"><tt class="py-docstring">    common, pre-defined queries.</tt> </tt>
<a name="L447"></a><tt class="py-lineno">447</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L448"></a><tt class="py-lineno">448</tt>  <tt class="py-line"><tt class="py-docstring">    An example of this may include having several models which each have images</tt> </tt>
<a name="L449"></a><tt class="py-lineno">449</tt>  <tt class="py-line"><tt class="py-docstring">    associated with them via ManyToOne relationships on other models. This may</tt> </tt>
<a name="L450"></a><tt class="py-lineno">450</tt>  <tt class="py-line"><tt class="py-docstring">    look something like this (showing only the image classes)::</tt> </tt>
<a name="L451"></a><tt class="py-lineno">451</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L452"></a><tt class="py-lineno">452</tt>  <tt class="py-line"><tt class="py-docstring">        ...</tt> </tt>
<a name="L453"></a><tt class="py-lineno">453</tt>  <tt class="py-line"><tt class="py-docstring">        class AImage(models.Model):</tt> </tt>
<a name="L454"></a><tt class="py-lineno">454</tt>  <tt class="py-line"><tt class="py-docstring">            a = models.ForeignKey(A)</tt> </tt>
<a name="L455"></a><tt class="py-lineno">455</tt>  <tt class="py-line"><tt class="py-docstring">            image = models.ImageField(...)</tt> </tt>
<a name="L456"></a><tt class="py-lineno">456</tt>  <tt class="py-line"><tt class="py-docstring">            public = models.BooleanField()</tt> </tt>
<a name="L457"></a><tt class="py-lineno">457</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L458"></a><tt class="py-lineno">458</tt>  <tt class="py-line"><tt class="py-docstring">        class BImage(models.Model):</tt> </tt>
<a name="L459"></a><tt class="py-lineno">459</tt>  <tt class="py-line"><tt class="py-docstring">            b = models.ForeignKey(B)</tt> </tt>
<a name="L460"></a><tt class="py-lineno">460</tt>  <tt class="py-line"><tt class="py-docstring">            image = models.ImageField(...)</tt> </tt>
<a name="L461"></a><tt class="py-lineno">461</tt>  <tt class="py-line"><tt class="py-docstring">            public = models.BooleanField()</tt> </tt>
<a name="L462"></a><tt class="py-lineno">462</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L463"></a><tt class="py-lineno">463</tt>  <tt class="py-line"><tt class="py-docstring">    As you can see, each model has a ``public`` boolean field. You may wish to</tt> </tt>
<a name="L464"></a><tt class="py-lineno">464</tt>  <tt class="py-line"><tt class="py-docstring">    specify managers for the public and non-public images for each. Using the</tt> </tt>
<a name="L465"></a><tt class="py-lineno">465</tt>  <tt class="py-line"><tt class="py-docstring">    ``QManager`` class, this would be done on each like so::</tt> </tt>
<a name="L466"></a><tt class="py-lineno">466</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L467"></a><tt class="py-lineno">467</tt>  <tt class="py-line"><tt class="py-docstring">        class AImage(models.Model):</tt> </tt>
<a name="L468"></a><tt class="py-lineno">468</tt>  <tt class="py-line"><tt class="py-docstring">            ...</tt> </tt>
<a name="L469"></a><tt class="py-lineno">469</tt>  <tt class="py-line"><tt class="py-docstring">            public_images = QManager(Q(public=True))</tt> </tt>
<a name="L470"></a><tt class="py-lineno">470</tt>  <tt class="py-line"><tt class="py-docstring">            non_public_images = ~public_images</tt> </tt>
<a name="L471"></a><tt class="py-lineno">471</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L472"></a><tt class="py-lineno">472</tt>  <tt class="py-line"><tt class="py-docstring">        class BImage(models.Model):</tt> </tt>
<a name="L473"></a><tt class="py-lineno">473</tt>  <tt class="py-line"><tt class="py-docstring">            ...</tt> </tt>
<a name="L474"></a><tt class="py-lineno">474</tt>  <tt class="py-line"><tt class="py-docstring">            public_images = QManager(Q(public=True))</tt> </tt>
<a name="L475"></a><tt class="py-lineno">475</tt>  <tt class="py-line"><tt class="py-docstring">            non_public_images = ~public_images</tt> </tt>
<a name="L476"></a><tt class="py-lineno">476</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L477"></a><tt class="py-lineno">477</tt>  <tt class="py-line"><tt class="py-docstring">    As you can see, the query ``Q(public=True)`` is repeated on each model</tt> </tt>
<a name="L478"></a><tt class="py-lineno">478</tt>  <tt class="py-line"><tt class="py-docstring">    definition. This violates the DRY principle, and so a solution is required</tt> </tt>
<a name="L479"></a><tt class="py-lineno">479</tt>  <tt class="py-line"><tt class="py-docstring">    if we are to keep code manageable. By using ``QManagerFactory``, this</tt> </tt>
<a name="L480"></a><tt class="py-lineno">480</tt>  <tt class="py-line"><tt class="py-docstring">    problem is solved. Somewhere in your models file (or elsewhere), the</tt> </tt>
<a name="L481"></a><tt class="py-lineno">481</tt>  <tt class="py-line"><tt class="py-docstring">    following should be added::</tt> </tt>
<a name="L482"></a><tt class="py-lineno">482</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L483"></a><tt class="py-lineno">483</tt>  <tt class="py-line"><tt class="py-docstring">        PublicImageManager = QManagerFactory(</tt> </tt>
<a name="L484"></a><tt class="py-lineno">484</tt>  <tt class="py-line"><tt class="py-docstring">            Q(public=True), name='PublicImageManager')</tt> </tt>
<a name="L485"></a><tt class="py-lineno">485</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L486"></a><tt class="py-lineno">486</tt>  <tt class="py-line"><tt class="py-docstring">    Then, on each model, the ``QManager`` definitions may be replaced by this::</tt> </tt>
<a name="L487"></a><tt class="py-lineno">487</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L488"></a><tt class="py-lineno">488</tt>  <tt class="py-line"><tt class="py-docstring">        class AImage(models.Model):</tt> </tt>
<a name="L489"></a><tt class="py-lineno">489</tt>  <tt class="py-line"><tt class="py-docstring">            ...</tt> </tt>
<a name="L490"></a><tt class="py-lineno">490</tt>  <tt class="py-line"><tt class="py-docstring">            public_images = PublicImageManager()</tt> </tt>
<a name="L491"></a><tt class="py-lineno">491</tt>  <tt class="py-line"><tt class="py-docstring">            non_public_images = ~public_images</tt> </tt>
<a name="L492"></a><tt class="py-lineno">492</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L493"></a><tt class="py-lineno">493</tt>  <tt class="py-line"><tt class="py-docstring">        class BImage(models.Model):</tt> </tt>
<a name="L494"></a><tt class="py-lineno">494</tt>  <tt class="py-line"><tt class="py-docstring">            ...</tt> </tt>
<a name="L495"></a><tt class="py-lineno">495</tt>  <tt class="py-line"><tt class="py-docstring">            public_images = PublicImageManager()</tt> </tt>
<a name="L496"></a><tt class="py-lineno">496</tt>  <tt class="py-line"><tt class="py-docstring">            non_public_images = ~public_images</tt> </tt>
<a name="L497"></a><tt class="py-lineno">497</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L498"></a><tt class="py-lineno">498</tt>  <tt class="py-line"><tt class="py-docstring">    By doing this, code adheres to DRY, and life is made easier for you, the</tt> </tt>
<a name="L499"></a><tt class="py-lineno">499</tt>  <tt class="py-line"><tt class="py-docstring">    developer, by saving space and time. For more information on how subclasses</tt> </tt>
<a name="L500"></a><tt class="py-lineno">500</tt>  <tt class="py-line"><tt class="py-docstring">    are constructed, consult this function's source code.</tt> </tt>
<a name="L501"></a><tt class="py-lineno">501</tt>  <tt class="py-line"><tt class="py-docstring">    """</tt> </tt>
<a name="L502"></a><tt class="py-lineno">502</tt>  <tt class="py-line">    <tt class="py-keyword">class</tt> <tt class="py-def-name">QManagerSubclass</tt><tt class="py-op">(</tt><tt class="py-base-class">QManager</tt><tt class="py-op">)</tt><tt class="py-op">:</tt> </tt>
<a name="L503"></a><tt class="py-lineno">503</tt>  <tt class="py-line">        <tt class="py-name">query</tt> <tt class="py-op">=</tt> <tt id="link-28" class="py-name"><a title="qmanager.get_valid_query" class="py-name" href="#" onclick="return doclink('link-28', 'get_valid_query', 'link-9');">get_valid_query</a></tt><tt class="py-op">(</tt><tt class="py-name">query</tt><tt class="py-op">)</tt> </tt>
</div><a name="L504"></a><tt class="py-lineno">504</tt>  <tt class="py-line">    <tt class="py-keyword">if</tt> <tt class="py-name">name</tt> <tt class="py-keyword">is</tt> <tt class="py-keyword">not</tt> <tt class="py-name">None</tt><tt class="py-op">:</tt> </tt>
<a name="L505"></a><tt class="py-lineno">505</tt>  <tt class="py-line">        <tt class="py-name">QManagerSubclass</tt><tt class="py-op">.</tt><tt class="py-name">__name__</tt> <tt class="py-op">=</tt> <tt class="py-name">name</tt> </tt>
<a name="L506"></a><tt class="py-lineno">506</tt>  <tt class="py-line">    <tt class="py-keyword">return</tt> <tt class="py-name">QManagerSubclass</tt> </tt>
</div><a name="L507"></a><tt class="py-lineno">507</tt>  <tt class="py-line"> </tt>
<a name="L508"></a><tt class="py-lineno">508</tt>  <tt class="py-line"> </tt>
<a name="get_query"></a><div id="get_query-def"><a name="L509"></a><tt class="py-lineno">509</tt> <a class="py-toggle" href="#" id="get_query-toggle" onclick="return toggle('get_query');">-</a><tt class="py-line"><tt class="py-keyword">def</tt> <a class="py-def-name" href="qmanager-module.html#get_query">get_query</a><tt class="py-op">(</tt><tt class="py-param">obj</tt><tt class="py-op">)</tt><tt class="py-op">:</tt> </tt>
</div><div id="get_query-collapsed" style="display:none;" pad="+++" indent="++++"></div><div id="get_query-expanded"><a name="L510"></a><tt class="py-lineno">510</tt>  <tt class="py-line">    <tt class="py-docstring">"""</tt> </tt>
<a name="L511"></a><tt class="py-lineno">511</tt>  <tt class="py-line"><tt class="py-docstring">    Given an object, return (somehow) a ``Q`` instance.</tt> </tt>
<a name="L512"></a><tt class="py-lineno">512</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L513"></a><tt class="py-lineno">513</tt>  <tt class="py-line"><tt class="py-docstring">    Usage and Implementation</tt> </tt>
<a name="L514"></a><tt class="py-lineno">514</tt>  <tt class="py-line"><tt class="py-docstring">    ========================</tt> </tt>
<a name="L515"></a><tt class="py-lineno">515</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L516"></a><tt class="py-lineno">516</tt>  <tt class="py-line"><tt class="py-docstring">    ``get_query`` accepts an object, and runs it through several tests to try</tt> </tt>
<a name="L517"></a><tt class="py-lineno">517</tt>  <tt class="py-line"><tt class="py-docstring">    and retrieve a query object. These tests are (in this order)::</tt> </tt>
<a name="L518"></a><tt class="py-lineno">518</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L519"></a><tt class="py-lineno">519</tt>  <tt class="py-line"><tt class="py-docstring">        1.  If the object is an instance of ``QManager``, return its ``query``</tt> </tt>
<a name="L520"></a><tt class="py-lineno">520</tt>  <tt class="py-line"><tt class="py-docstring">            attribute.</tt> </tt>
<a name="L521"></a><tt class="py-lineno">521</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L522"></a><tt class="py-lineno">522</tt>  <tt class="py-line"><tt class="py-docstring">        2.  If the object is an instance of ``django.db.models.Manager``, and</tt> </tt>
<a name="L523"></a><tt class="py-lineno">523</tt>  <tt class="py-line"><tt class="py-docstring">            we are using the old version of Django, get its query set, and</tt> </tt>
<a name="L524"></a><tt class="py-lineno">524</tt>  <tt class="py-line"><tt class="py-docstring">            return the ``_filters`` attribute on the ``QuerySet`` instance.</tt> </tt>
<a name="L525"></a><tt class="py-lineno">525</tt>  <tt class="py-line"><tt class="py-docstring">        </tt> </tt>
<a name="L526"></a><tt class="py-lineno">526</tt>  <tt class="py-line"><tt class="py-docstring">        3.  If the object is a ``QuerySet`` instance, and we are using the old</tt> </tt>
<a name="L527"></a><tt class="py-lineno">527</tt>  <tt class="py-line"><tt class="py-docstring">            (pre-1.0) version of Django, return its ``_filters`` attribute.</tt> </tt>
<a name="L528"></a><tt class="py-lineno">528</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L529"></a><tt class="py-lineno">529</tt>  <tt class="py-line"><tt class="py-docstring">    If none of these tests succeed, the object is returned as-is. This</tt> </tt>
<a name="L530"></a><tt class="py-lineno">530</tt>  <tt class="py-line"><tt class="py-docstring">    indicates either that the object is already a ``Q`` instance, or that it is</tt> </tt>
<a name="L531"></a><tt class="py-lineno">531</tt>  <tt class="py-line"><tt class="py-docstring">    of an unknown type.</tt> </tt>
<a name="L532"></a><tt class="py-lineno">532</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L533"></a><tt class="py-lineno">533</tt>  <tt class="py-line"><tt class="py-docstring">    This function does not validate that objects returned are, in fact, ``Q``</tt> </tt>
<a name="L534"></a><tt class="py-lineno">534</tt>  <tt class="py-line"><tt class="py-docstring">    instances. For validation, see the ``get_valid_query`` function.</tt> </tt>
<a name="L535"></a><tt class="py-lineno">535</tt>  <tt class="py-line"><tt class="py-docstring">    """</tt> </tt>
<a name="L536"></a><tt class="py-lineno">536</tt>  <tt class="py-line">    <tt class="py-keyword">if</tt> <tt class="py-name">isinstance</tt><tt class="py-op">(</tt><tt class="py-name">obj</tt><tt class="py-op">,</tt> <tt id="link-29" class="py-name"><a title="qmanager.QManager" class="py-name" href="#" onclick="return doclink('link-29', 'QManager', 'link-11');">QManager</a></tt><tt class="py-op">)</tt><tt class="py-op">:</tt> </tt>
<a name="L537"></a><tt class="py-lineno">537</tt>  <tt class="py-line">        <tt class="py-keyword">return</tt> <tt class="py-name">obj</tt><tt class="py-op">.</tt><tt class="py-name">query</tt> </tt>
<a name="L538"></a><tt class="py-lineno">538</tt>  <tt class="py-line">    <tt class="py-keyword">elif</tt> <tt class="py-name">isinstance</tt><tt class="py-op">(</tt><tt class="py-name">obj</tt><tt class="py-op">,</tt> <tt class="py-name">Manager</tt><tt class="py-op">)</tt> <tt class="py-keyword">and</tt> <tt id="link-30" class="py-name"><a title="qmanager.OLD_VERSION" class="py-name" href="#" onclick="return doclink('link-30', 'OLD_VERSION', 'link-0');">OLD_VERSION</a></tt><tt class="py-op">:</tt> </tt>
<a name="L539"></a><tt class="py-lineno">539</tt>  <tt class="py-line">        <tt class="py-keyword">return</tt> <tt class="py-name">obj</tt><tt class="py-op">.</tt><tt id="link-31" class="py-name"><a title="qmanager.QManager.get_query_set" class="py-name" href="#" onclick="return doclink('link-31', 'get_query_set', 'link-24');">get_query_set</a></tt><tt class="py-op">(</tt><tt class="py-op">)</tt><tt class="py-op">.</tt><tt class="py-name">_filters</tt> </tt>
<a name="L540"></a><tt class="py-lineno">540</tt>  <tt class="py-line">    <tt class="py-keyword">elif</tt> <tt class="py-name">isinstance</tt><tt class="py-op">(</tt><tt class="py-name">obj</tt><tt class="py-op">,</tt> <tt class="py-name">QuerySet</tt><tt class="py-op">)</tt> <tt class="py-keyword">and</tt> <tt id="link-32" class="py-name"><a title="qmanager.OLD_VERSION" class="py-name" href="#" onclick="return doclink('link-32', 'OLD_VERSION', 'link-0');">OLD_VERSION</a></tt><tt class="py-op">:</tt> </tt>
<a name="L541"></a><tt class="py-lineno">541</tt>  <tt class="py-line">        <tt class="py-keyword">return</tt> <tt class="py-name">obj</tt><tt class="py-op">.</tt><tt class="py-name">_filters</tt> </tt>
<a name="L542"></a><tt class="py-lineno">542</tt>  <tt class="py-line">    <tt class="py-keyword">return</tt> <tt class="py-name">obj</tt> </tt>
</div><a name="L543"></a><tt class="py-lineno">543</tt>  <tt class="py-line"> </tt>
<a name="L544"></a><tt class="py-lineno">544</tt>  <tt class="py-line"> </tt>
<a name="get_valid_query"></a><div id="get_valid_query-def"><a name="L545"></a><tt class="py-lineno">545</tt> <a class="py-toggle" href="#" id="get_valid_query-toggle" onclick="return toggle('get_valid_query');">-</a><tt class="py-line"><tt class="py-keyword">def</tt> <a class="py-def-name" href="qmanager-module.html#get_valid_query">get_valid_query</a><tt class="py-op">(</tt><tt class="py-param">query</tt><tt class="py-op">)</tt><tt class="py-op">:</tt> </tt>
</div><div id="get_valid_query-collapsed" style="display:none;" pad="+++" indent="++++"></div><div id="get_valid_query-expanded"><a name="L546"></a><tt class="py-lineno">546</tt>  <tt class="py-line">    <tt class="py-docstring">"""</tt> </tt>
<a name="L547"></a><tt class="py-lineno">547</tt>  <tt class="py-line"><tt class="py-docstring">    Given an object, return a ``Q`` instance, or raise an error.</tt> </tt>
<a name="L548"></a><tt class="py-lineno">548</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L549"></a><tt class="py-lineno">549</tt>  <tt class="py-line"><tt class="py-docstring">    Introduction</tt> </tt>
<a name="L550"></a><tt class="py-lineno">550</tt>  <tt class="py-line"><tt class="py-docstring">    ============</tt> </tt>
<a name="L551"></a><tt class="py-lineno">551</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L552"></a><tt class="py-lineno">552</tt>  <tt class="py-line"><tt class="py-docstring">    ``get_valid_query`` works by calling ``get_query`` on the provided object.</tt> </tt>
<a name="L553"></a><tt class="py-lineno">553</tt>  <tt class="py-line"><tt class="py-docstring">    The returned object is then examined using ``isinstance``. If it is not an</tt> </tt>
<a name="L554"></a><tt class="py-lineno">554</tt>  <tt class="py-line"><tt class="py-docstring">    instance of ``django.db.models.query.Q``, then a ``TypeError`` is raised.</tt> </tt>
<a name="L555"></a><tt class="py-lineno">555</tt>  <tt class="py-line"><tt class="py-docstring">    Otherwise, the object is returned.</tt> </tt>
<a name="L556"></a><tt class="py-lineno">556</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L557"></a><tt class="py-lineno">557</tt>  <tt class="py-line"><tt class="py-docstring">    If using a version of Django below 1.0, then ``QOperator`` will be</tt> </tt>
<a name="L558"></a><tt class="py-lineno">558</tt>  <tt class="py-line"><tt class="py-docstring">    considered a valid superclass as well. Prior to Django v1.0, the and's,</tt> </tt>
<a name="L559"></a><tt class="py-lineno">559</tt>  <tt class="py-line"><tt class="py-docstring">    or's and not's of ``Q`` instances were represented by instances of</tt> </tt>
<a name="L560"></a><tt class="py-lineno">560</tt>  <tt class="py-line"><tt class="py-docstring">    ``QAnd``, ``QOr`` and ``QNot`` respectively. The first two are subclasses</tt> </tt>
<a name="L561"></a><tt class="py-lineno">561</tt>  <tt class="py-line"><tt class="py-docstring">    of ``QOperator``, the third of ``Q`` itself. By testing for subclasses of</tt> </tt>
<a name="L562"></a><tt class="py-lineno">562</tt>  <tt class="py-line"><tt class="py-docstring">    ``QOperator`` (only with the old version of Django), all query types are</tt> </tt>
<a name="L563"></a><tt class="py-lineno">563</tt>  <tt class="py-line"><tt class="py-docstring">    encompassed.</tt> </tt>
<a name="L564"></a><tt class="py-lineno">564</tt>  <tt class="py-line"><tt class="py-docstring">    </tt> </tt>
<a name="L565"></a><tt class="py-lineno">565</tt>  <tt class="py-line"><tt class="py-docstring">    By returning the query, it allows this function to be used wherever a valid</tt> </tt>
<a name="L566"></a><tt class="py-lineno">566</tt>  <tt class="py-line"><tt class="py-docstring">    query is required, eliminating a small amount of boilerplate from the</tt> </tt>
<a name="L567"></a><tt class="py-lineno">567</tt>  <tt class="py-line"><tt class="py-docstring">    definition from ``QManager``.</tt> </tt>
<a name="L568"></a><tt class="py-lineno">568</tt>  <tt class="py-line"><tt class="py-docstring">    """</tt> </tt>
<a name="L569"></a><tt class="py-lineno">569</tt>  <tt class="py-line">    <tt class="py-name">q</tt> <tt class="py-op">=</tt> <tt id="link-33" class="py-name" targets="Function qmanager.get_query()=qmanager-module.html#get_query"><a title="qmanager.get_query" class="py-name" href="#" onclick="return doclink('link-33', 'get_query', 'link-33');">get_query</a></tt><tt class="py-op">(</tt><tt class="py-name">query</tt><tt class="py-op">)</tt> </tt>
<a name="L570"></a><tt class="py-lineno">570</tt>  <tt class="py-line">    <tt class="py-keyword">if</tt> <tt id="link-34" class="py-name"><a title="qmanager.OLD_VERSION" class="py-name" href="#" onclick="return doclink('link-34', 'OLD_VERSION', 'link-0');">OLD_VERSION</a></tt><tt class="py-op">:</tt> </tt>
<a name="L571"></a><tt class="py-lineno">571</tt>  <tt class="py-line">        <tt class="py-name">valid_classes</tt> <tt class="py-op">=</tt> <tt class="py-op">(</tt><tt class="py-name">Q</tt><tt class="py-op">,</tt> <tt class="py-name">QOperator</tt><tt class="py-op">)</tt> </tt>
<a name="L572"></a><tt class="py-lineno">572</tt>  <tt class="py-line">    <tt class="py-keyword">else</tt><tt class="py-op">:</tt> </tt>
<a name="L573"></a><tt class="py-lineno">573</tt>  <tt class="py-line">        <tt class="py-name">valid_classes</tt> <tt class="py-op">=</tt> <tt class="py-name">Q</tt> </tt>
<a name="L574"></a><tt class="py-lineno">574</tt>  <tt class="py-line">    <tt class="py-keyword">if</tt> <tt class="py-keyword">not</tt> <tt class="py-name">isinstance</tt><tt class="py-op">(</tt><tt class="py-name">q</tt><tt class="py-op">,</tt> <tt class="py-name">valid_classes</tt><tt class="py-op">)</tt><tt class="py-op">:</tt> </tt>
<a name="L575"></a><tt class="py-lineno">575</tt>  <tt class="py-line">        <tt class="py-keyword">raise</tt> <tt class="py-name">TypeError</tt><tt class="py-op">(</tt><tt class="py-string">'Not a query object: %r'</tt> <tt class="py-op">%</tt> <tt class="py-op">(</tt><tt class="py-name">query</tt><tt class="py-op">,</tt><tt class="py-op">)</tt><tt class="py-op">)</tt> </tt>
<a name="L576"></a><tt class="py-lineno">576</tt>  <tt class="py-line">    <tt class="py-keyword">return</tt> <tt class="py-name">q</tt> </tt>
</div><a name="L577"></a><tt class="py-lineno">577</tt>  <tt class="py-line"> </tt><script type="text/javascript">
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